Add support for cucumber

[jrluis]

Hi,

I've been planning on adding a cucumber runner.

The ideia is to add some flags that control which files get sent as task. That way we could execute only rspec or only cucumber or both.

In the following images I've identified the spots where changes will be made.

What do you think about this plan to implement cucumber support?

[sorah]

Since we're not using Cucumber, we can't have strong support on Cucumber, and we don't have a plan to do so.
But if you can send us a pull request, we can review your implementation. (but remember I can't promise it can be merged or not)