Add release task

Added the `release` task. If you run `grunt release:VERSION`, the release process will be automated. It'll build the files, update the manifests, tag the commit, update the published assets, and update the version number on http://twitter.github.com/typeahead.js/. It even checks to make sure your working directory isn't dirty and that the version passed in is valid.

Also added the manifest needed for the jQuery plugin repo #1 and removed `dist` from *.gitignore* for bower compatibility #10.