Fix #69: include active_support before requiring core_ext

Known issue w/ active_support:

https://github.com/rails/rails/issues/14664
Merge pull request #74 from ManageIQ/activesupport-dep

Fix #69: include active_support before requiring core_ext
Relax polisher deps, gracefully fail if missing (rev 3)

Now polisher gem contains minimal runtime deps w/ mechanism
to catch runtime load errors. Components missing reqs will
not be accessible / calling methods on them will indicate
to install optional dependencies

Rebased against latest master