Ignore generated CSS files in the repository tree
Make sure a more recent compass is present by installing as a gem

This is based on sayit.mysociety.org's post_deploy_actions.bash
Strip some trailing whitespace
Make sure there are no newlines before the doctype

While newlines are allowed before the doctype, [1] this will make
older versions of IE switch to quirks mode, so it's best to avoid it.

[1] http://www.w3.org/TR/html-markup/documents.html#conformant-documents