Add support for Django REST Framework 3.8.x

[sliverc]

No code changes needed.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added (no code changes)
• documentation updated
• changelog entry added to CHANGELOG.md
• author name in AUTHORS

[codecov-io]

Codecov Report

Merging #441 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #441   +/-   ##
======================================
  Coverage    92.6%   92.6%           
======================================
  Files          54      54           
  Lines        2812    2812           
======================================
  Hits         2604    2604           
  Misses        208     208

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[mblayman]

👍 There is also a place in the getting started docs that references DRF that should probably be updated too. Otherwise, this looks good to me.

[sliverc]

Thanks. Also added version to getting started guide. Merging.