Update forcetk.js to support Windows8 in phonegap

Protocol in Windows8 app is ms-appx: not file:

Author: hdramos

forcetk.js

@@ -59,7 +59,7 @@ if (forcetk.Client === undefined) {
         this.clientId = clientId;
         this.loginUrl = loginUrl || 'https://login.salesforce.com/';
         if (typeof proxyUrl === 'undefined' || proxyUrl === null) {
-            if (location.protocol === 'file:') {
+            if (location.protocol === 'file:' || location.protocol === 'ms-appx:') {
                 // In PhoneGap
                 this.proxyUrl = null;
             } else {
@@ -484,4 +484,4 @@ if (forcetk.Client === undefined) {
         return this.ajax('/' + this.apiVersion + '/search?q=' + escape(sosl)
         , callback, error);
     }
-}
+}