Fix 1063154 - Add API endpoint for generating MDN compat table

The /api/v1/view_features endpoint returns the related resources needed to generate an MDN compat table.  For example, this simple Browser Compatibility table:

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#Browser_compatibility

is represented with this JSON

http://doesitwork-dev.allizom.org/api/v1/view_features/2423

This PR does not include work to [import correct MDN data](https://bugzilla.mozilla.org/show_bug.cgi?id=1079920) or [generating HTML](https://bugzilla.mozilla.org/show_bug.cgi?id=1077879), but work can start on those soon.

This includes the changes in PR #12.