Refactoring

Various changes to clean up / simplify / improve the code.

Some highlights:

* put facebook/twitter stuff in mustache templates so we don't have a bunch of duplicated / hidden code in the html
* eliminated an ajax call on page load by passing in some data via a script tag in the html; this also simplified the js code
* scopes on EventItem model for easy querying
* updates to work with Legistar API change
* updates date window for fetching Legistar data