feat(cucumber): Process the Cucumber 'coffee' param

Usage:

```javascript
// In the protractor config:
exports.config = {
  // don't forget your own config

  framework: "cucumber",
  // Options to be passed to Cucumber
  cucumberOpts: {
    coffee: true // display step definition snippets in CoffeeScript
  }
};
```

Assuming that you run a Cucumber feature with the step `I want to test something else` and do not define its implementation yet.

You will see that the step implementation is now in CoffeeScript instead of JavaScript after running protractor:

> You can implement step definitions for undefined steps with these snippets:
  ```coffeescript
  @Then /^I want to test something else$/, (callback) ->
    # Write code here that turns the phrase above into concrete actions
    callback.pending()
  ```
Ok, done.