Push built docs to remote gh-pages

[jb-adams]

Is the goal with this app ultimately to push the built docs back to the gh-pages remote branch? Currently, the app:

1. pulls the remote gh-pages
2. builds docs based on the current branch, overwriting any files that may previously exist in gh-pages with the same filename

Do we also want to commit and push the updated docs tree back to gh-pages at the origin?

[tschaffter]

See #47 (comment)