[#30] Upgrade Twitter Bootstrap to latest version

Trello: https://trello.com/c/FDzEZ8JI

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We use Twitter Bootstrap for the grid system and responsive layouts.  Other versions of the library are floating around, and it's not clear which version we are currently using.

This branch removes the ambiguity by removing any unused bootstraps and upgrading the file we're using to the latest version.

In addition, the css is currently minified.  This has been replaced with an minified version which makes it easier to process in development and easier to upgrade (try figuring out the diff of a minified script...). Since we're using sprockets, the css is minified anyway in production.