Update introduction.md

Updated text.
Define front-end library dependencies

Define front-end dependencies using a bower.json file.  For now
don't load/copy files using Bower, just load them from a CDN.
Backbone collections for providers

Scaffolding for Backbone collections with methods for faceting.

Add basic Mocha-based tests for collection methods.
Merge remote-tracking branch 'origin/master'
Put all application-specific JS in one file

I don't think there will be enough code to warrant the cruft of
RequireJS, but it seemed nice to be able to load the code in either
the browser or Node, which would mean lots of repeated boilerplate.

For now, just put everything in one file and factor it out again if
it needed.
Data-driven select filter view
Add data and js directories to clean task
Move footer scripts to YFM
Offcanvas toggling of filters
Merge branch 'offcanvas' into gh-pages
Deploy offcanvas