Support `default_action` on multiple Chef versions.

- Fixes #3
Move to Strainer for testing and test against multiple Chef versions
Don't test on Ruby 1.8.7 or ree because of Celluloid
Also support multiple Chef versions on `magic_shell_environment`

- Fixes #3
Don't test against ruby-head.

No one should be running Chef against ruby-head.
Add specs
Fix specs
Can't test on Ruby 2.0 yet
Fix formatting in Gemfile
Merge pull request #4 from customink-webops/fix_tests

Fix tests