This patch adds the gh-pages task and configs it to create a directory 'public_html'.

The public_html directory contains the gh-pages branch files with the files from the src branch dist directory.

I also added a task that creates a Gemfile in the public_html directory so a developer can get Jekyll running against the directory quickly. We might want to add a task that cds into this new dir and starts Jekyll automatically.

We can change the configuration of the gh-pages task to push to the origin/gh-pages branch. Better would be to pass a flag when calling grunt publish that indicates the changes should be pushed to the remote branch, but I'm not sure how to do that yet.