Update selects based on facet, show count

Update the options in the select dropdowns to show only available
options after the facet has been performed.

We might not want to do this on some values, like provider.

Add a counter of the number of results, which also toggles the
offcanvas sidebar back to the results list.
Add search

Add search using lunr.js.  Right now the search is just on the
provider name, but it would be easy to add other fields to the
index.

http://blog.apps.chicagotribune.com/2014/02/17/nuts-and-bolts-of-event-listings/
was extremely helpful.

Add a method to the Providers collection to reset filters and
trigger a unified ``filter`` event on either search or facet in
addition to explicit ``search`` and ``facet`` events.
Merge branch 'master' into gh-pages
Rebuild.