Revert bundler_ext commits.

https://bugzilla.redhat.com/show_bug.cgi?id=1122279

b3d6bd6c: bundler_ext integration (rev 3)
0276a23e: Warn and fallback to bundler when bundler_ext variables are not set.
Merge pull request #491 from jrafanie/revert_bundler_ext

Revert bundler_ext commits.