Add drupal to list of not square social icons

Add 'drupal' to the list of not square icons as a *-square version
of fa-drupal is not available in the current version of Font
Awesome (4.2).
Article changelog

If GITHUB_REPO_URL is specified a link to the GitHub history page is
included below each article.

In addition, a changelog may be included at the bottom of the article by
using the metadata keyword 'Changelog' of which there may be multiple
occurrences.