Fix for rails 3 2 stable

Hey!

So we found a bug when running jasmine-rails against rails `3.2.13.rc1`

In previous versions of rails `3.x`, you were able to pass in absolute file paths to `javascript_include_tag` and it would "just work". In rails `3.2.13.rc1`, that "feature" has been removed.

In this change, I ensure we pass logical paths to the include_tag helpers. So instead of passing: `/Users/keithpitt/project-name/spec/javascripts/some_spec.js.coffee.js` we pass `some_spec.js.coffee.js`.

This change has been tested on rails `3.2.12` and `3.2.13.rc1`

Thanks!