Use REST API call to fetch source and translation text.

This is not a final implementation, as much of the fetched data still
needs to be cached. The caching will be added while looking at paging
and infinite-scroll options since these will inform what is an appropriate
structure for cached data.
Merge branch 'master' into phrases-from-api

Conflicts:
	app/editor/EditorCtrl.js
Merge pull request #32 from zanata/phrases-from-api

User REST API to fetch source and translation text