Added a little map to the index page. Based on the
center of the map, displays the questions (based
on Dennis' backend code) for which the center is
within the radius. Automatically updates when
the map center changes.

Needs to be updated once Dennis updates his code
to get all the questions for a bounding box, not
just the center.

Right now, just displays all possible questions
at the bottom of the page.
Added filter.js to header.
Removed filter from head and added it to application.js.
fixed heroku merge conflicts