Update CLI method descriptions
Prompt for each outdated gem

* Add highline
Require ruby 1.9.3+
Implement CLI#outdated

* Move repo finder, open, version lookup into OutdatedGem
* Add CLI parameters
* Remove :no_skip from CLI#outdated
Add OutdatedGem#compare

* Fix OutdatedGem#load_bundle_versions
* Add OutdatedGemTest
Version 0.0.2