Fixes #7233 - Drop Ruby 1.8.7 and revert Ruby 1.8.7 specifics

- [x] rake test passed
- [x] rails server loaded and function correctly
- [x] Ubuntu 12.04 packaging blocker issue 
- [x] drop 1.8.7 tests on Jenkins
Could we keep this at ~> 0.8.0 for now please, due to https://github.com/grosser/fast_gettext/issues/70?  It invalidates much of our packaging, which I'd rather not delete if it gets fixed later.