Remove last vestiges of Ruby 1.8.7 support

We dropped support for Ruby 1.8.7 in Overcommit 0.14.0, but didn't get
around to updating the codebase to use Ruby 1.9 hashes and other such
style changes.

Change-Id: I9e86d4b2094a8bcb9a26b8e0863836bdda34be62
Reviewed-on: http://gerrit.causes.com/45275
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>