Add Travis-CI test environment
Run extra tasks on only MRI && >= 1.9.3
Add assert failure messages to some tests.
Add helper assert methods for more consistent and descriptive messages, and for test conciseness.
Fix a variable name.
Merge pull request #27 from otahi/improve_travis_ci_tests

[WIP] Improve travis ci tests
Removing Ruby 1.8 from tests
Merge pull request #29 from keithrbennett/add-assert-messages

Add assert failure messages to some tests.