Build pipeline

This branch adds a build pipeline based on [Grunt](http://gruntjs.com/) which will give us much more flexibility in working on the site in the future. After merging this branch, the built site will reside in the `/build` folder while the site assets that are used to build that site will be in `/banjir`.

The current build tasks I've set up do a few things:

- `grunt` builds the entire site
- `grunt assets` compiles the site's CSS and JS files into single, minified files.
- `grunt site` fills in the site's HTML templates with strings for each of the various translations available, with the output in `/build/:language`.
- `grunt watch` watches for changes in the `assets` directory and rebuilds the site when they change. Useful during development.
- `grunt server` builds the site and launches a barebones server to serve up files in the `\build` directory. This command also concurrently runs the `watch` command to update files as they change.

I've also added instructions on how to run these tasks to the _README_ for other developers.