update tweet schema to save the handle group the tweet handle belongs to, sourced from following DB table. closes #24
if tweet is RT, set handle_group to the group of RTer who we are following, not to the handle of the original tweet
Merge branch 'dev' of https://github.com/sosolimited/Biomed-Backend into dev

Conflicts:
	app/twitter.js
turn off a console.log left in Twitter
Add Group functionality for backbone models. Closes #13
when adding new group, render it in edit mode when first added to collection
wrap storage.getEnabledFilters() in callback for Twitter instantiation
fixed chrome bug with saving models, fixed #27