Remove Ruby 1.9.2 support, add Ruby 2.0.0 support, fix Travis build

**As** a developer 
**In order to** feel comfortable when adding or refactoring steps 
**I want** the Travis build to be always successful. 

Hello!

I saw the [Anthony Eden talk](http://vimeo.com/30586709), and loved to find this gem. The steps testing is ver fine :D ! However the broken Travis build made me a bit uncomfortable; here is some code to fix it.

I borrowed a commit from @legolin [#18](https://github.com/jayzes/cucumber-api-steps/pull/18), IMHO it fits better here than with the step contributions @legolin did (which are worth the PR by themselves).

I added some thoughts to the commits below in order to support the decisions I've made, if you have any comments I'll be glad to read them.

Best regards!