Bower support, multiple jQuery versions

This pull request uses Bower to install Qunit, jQuery and Zepto and introduces a jQuery legacy (1.10) configuration (as mentioned in #526) and removes supported libraries from being checked directly into the repository.

`bower install` will run as an NPM post-install script. Although this is considered to be an anti pattern this should be ok here as NPM is only used for development. Re-run `npm install` after updating from this PR to get the bower components.