Update asset fingerprinting information

- Replaced MD5 => SHA256 where necessary
- Updated sprockets manifest example

See: https://github.com/rails/sprockets/blob/dd9b3b53c06c602c49057bc4a426c1a446ed7a4a/lib/sprockets.rb#L26

Author: zachahn

guides/source/asset_pipeline.md

@@ -78,9 +78,9 @@ requests can mean faster loading for your application.
 Sprockets concatenates all JavaScript files into one master `.js` file and all
 CSS files into one master `.css` file. As you'll learn later in this guide, you
 can customize this strategy to group files any way you like. In production,
-Rails inserts an MD5 fingerprint into each filename so that the file is cached
-by the web browser. You can invalidate the cache by altering this fingerprint,
-which happens automatically whenever you change the file contents.
+Rails inserts an SHA256 fingerprint into each filename so that the file is
+cached by the web browser. You can invalidate the cache by altering this
+fingerprint, which happens automatically whenever you change the file contents.
 
 The second feature of the asset pipeline is asset minification or compression.
 For CSS files, this is done by removing whitespace and comments. For JavaScript,
@@ -346,9 +346,9 @@ Provided that the pipeline is enabled within your application (and not disabled
 in the current environment context), this file is served by Sprockets. If a file
 exists at `public/assets/rails.png` it is served by the web server.
 
-Alternatively, a request for a file with an MD5 hash such as
-`public/assets/rails-af27b6a414e6da00003503148be9b409.png` is treated the same
-way. How these hashes are generated is covered in the [In
+Alternatively, a request for a file with an SHA256 hash such as
+`public/assets/rails-f90d8a84c707a8dc923fca1ca1895ae8ed0a09237f6992015fef1e11be77c023.png`
+is treated the same way. How these hashes are generated is covered in the [In
 Production](#in-production) section later on in this guide.
 
 Sprockets will also look through the paths specified in `config.assets.paths`,
@@ -654,7 +654,7 @@ In the production environment Sprockets uses the fingerprinting scheme outlined
 above. By default Rails assumes assets have been precompiled and will be
 served as static assets by your web server.
 
-During the precompilation phase an MD5 is generated from the contents of the
+During the precompilation phase an SHA256 is generated from the contents of the
 compiled files, and inserted into the filenames as they are written to disk.
 These fingerprinted names are used by the Rails helpers in place of the manifest
 name.
@@ -743,22 +743,24 @@ Rails.application.config.assets.precompile += %w( admin.js admin.css )
 NOTE. Always specify an expected compiled filename that ends with .js or .css,
 even if you want to add Sass or CoffeeScript files to the precompile array.
 
-The task also generates a `manifest-md5hash.json` that contains a list with
-all your assets and their respective fingerprints. This is used by the Rails
-helper methods to avoid handing the mapping requests back to Sprockets. A
-typical manifest file looks like:
+The task also generates a `.sprockets-manifest-md5hash.json` (where `md5hash` is
+a MD5 hash) that contains a list with all your assets and their respective
+fingerprints. This is used by the Rails helper methods to avoid handing the
+mapping requests back to Sprockets. A typical manifest file looks like:
 
 ```ruby
-{"files":{"application-723d1be6cc741a3aabb1cec24276d681.js":{"logical_path":"application.js","mtime":"2013-07-26T22:55:03-07:00","size":302506,
-"digest":"723d1be6cc741a3aabb1cec24276d681"},"application-12b3c7dd74d2e9df37e7cbb1efa76a6d.css":{"logical_path":"application.css","mtime":"2013-07-26T22:54:54-07:00","size":1560,
-"digest":"12b3c7dd74d2e9df37e7cbb1efa76a6d"},"application-1c5752789588ac18d7e1a50b1f0fd4c2.css":{"logical_path":"application.css","mtime":"2013-07-26T22:56:17-07:00","size":1591,
-"digest":"1c5752789588ac18d7e1a50b1f0fd4c2"},"favicon-a9c641bf2b81f0476e876f7c5e375969.ico":{"logical_path":"favicon.ico","mtime":"2013-07-26T23:00:10-07:00","size":1406,
-"digest":"a9c641bf2b81f0476e876f7c5e375969"},"my_image-231a680f23887d9dd70710ea5efd3c62.png":{"logical_path":"my_image.png","mtime":"2013-07-26T23:00:27-07:00","size":6646,
-"digest":"231a680f23887d9dd70710ea5efd3c62"}},"assets":{"application.js":
-"application-723d1be6cc741a3aabb1cec24276d681.js","application.css":
-"application-1c5752789588ac18d7e1a50b1f0fd4c2.css",
-"favicon.ico":"favicona9c641bf2b81f0476e876f7c5e375969.ico","my_image.png":
-"my_image-231a680f23887d9dd70710ea5efd3c62.png"}}
+{"files":{"application-aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b.js":{"logical_path":"application.js","mtime":"2016-12-23T20:12:03-05:00","size":412383,
+"digest":"aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b","integrity":"sha256-ruS+cfEogDeueLmX3ziDMu39JGRxtTPc7aqPn+FWRCs="},
+"application-86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18.css":{"logical_path":"application.css","mtime":"2016-12-23T19:12:20-05:00","size":2994,
+"digest":"86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18","integrity":"sha256-hqKStQcHk8N+LA5fOfc7s4dkTq6tp/lub8BAoCixbBg="},
+"favicon-8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda.ico":{"logical_path":"favicon.ico","mtime":"2016-12-23T20:11:00-05:00","size":8629,
+"digest":"8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda","integrity":"sha256-jSOHuNTTLOzZP6OQDfDp/4nQGqzYT1DngMF8n2s9Dto="},
+"my_image-f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493.png":{"logical_path":"my_image.png","mtime":"2016-12-23T20:10:54-05:00","size":23414,
+"digest":"f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493","integrity":"sha256-9AKBVv1+ygNYTV8vwEcN8eDbxzaequY4sv8DP5iOxJM="}},
+"assets":{"application.js":"application-aee4be71f1288037ae78b997df388332edfd246471b533dcedaa8f9fe156442b.js",
+"application.css":"application-86a292b5070793c37e2c0e5f39f73bb387644eaeada7f96e6fc040a028b16c18.css",
+"favicon.ico":"favicon-8d2387b8d4d32cecd93fa3900df0e9ff89d01aacd84f50e780c17c9f6b3d0eda.ico",
+"my_image.png":"my_image-f4028156fd7eca03584d5f2fc0470df1e0dbc7369eaae638b2ff033f988ec493.png"}}
 ```
 
 The default location for the manifest is the root of the location specified in
@@ -850,7 +852,7 @@ config.assets.compile = true
 
 On the first request the assets are compiled and cached as outlined in
 development above, and the manifest names used in the helpers are altered to
-include the MD5 hash.
+include the SHA256 hash.
 
 Sprockets also sets the `Cache-Control` HTTP header to `max-age=31536000`. This
 signals all caches between your server and the client browser that this content