progressive-loading-api-client: Proof-of-concept functioning api client with progressive loading.  Missing tests.
Merge branch 'progressive-loading-api' into progressive-loading-api-client

Conflicts:
	search/views/search.py
	static/js/languagelearning.main.js
	static/js/routers/languagelearning.js
	utils/api.py

Merging in updates from code review on `progressive-loading-api`, and bringing
the client code up to spec.  Also some cleanup besides.

Still missing client tests- those are next.
progressive-loading-api-client:

Added client tests for progressive loading.  Also updated sinon.js.
Merge pull request #28 from antoviaque/progressive-loading-api-client

progressive-loading-api-client: Proof-of-concept functioning api client ...