Build with different major chef versions.
Add rake task and remove explicit travis test runner.

Previous test runner was missing a test file.
Test with 1.x Rubygems.

https://github.com/rubygems/rubygems/issues/502
Add treetop as test dependency.
Fix missing argument for RunContext.
Advertise chef version before build.
Merge pull request #29 from pawelpacana/travis

Fix travis tests