Add in functionality for viewing by tags.
Add a service for accessing the materialscommons database. This is a thin wrapper around cornercouch that hides the boilerplate.
Update to add in tags, including new views.
Cleanup pages by moving headings around.
Merge branch 'v3' into trymerge

Conflicts:
	assets/js/materialscommons/materialscommons-app.js
	partials/user_functions.html