Enable gulp as a generation-time flag

[Awk34]

I want to get the gulpfile support in, but it just isn't complete enough yet. I thought of a good solution: Add a --gulp flag to the generator. That way users won't be asked if they want Gulp at generation-time, since I don't want to add a very less-than-complete feature to the prompts list, but a user can still use a flag if he/she really wants the gulpfile to be generated.

[tmundt]

If I may ask, is GULP support included as described? Could there be another using GULP instead of GRUNT?

[Awk34]

@tmundt yes, Gulp support was turned on as a flag in 3.1.0