Create gherkin syntax highlighting for Ace

[eliza411]

Feature: Highlight syntax in code editor
In order to easily see the structure of a feature file
As a web user
I want to see Gherkin syntax highlighting

[eliza411]

I've integrated Ace and rudimentary syntax highlighting by forking https://github.com/norzechowicz/aceeditor-bundle and including mode-gherkin-en.js (for the time being) in the Ace source included with this bundle (from here: https://github.com/cucumber/gherkin-syntax-highlighters). There's a lot left to do:

I'd like to see the given, when, and then blocks highlighted in different colors, more like the command-line output and to see well-supported translation. It demo-able though.