Bump version to 0.2.2

- Support ruby version 1.9.3+ onward
- Use 'activesupport-core-ext' instead of 'agile_utils'
Bump version to 0.2.3

- Merge pull request from [Nick den Engelsman](https://github.com/nicka)
- Add Rspec support for testing framework (default to minitest)
- Minor code cleanup/refactoring