Gulp intermediate rewrite, fixes 53, 54, and 55

Could use some code review here. Special note:

- sourcemap path change / regression in 2514808
- speed up Sass command: 63c396f. Cool/not cool?
- tests: how much to test, how little?

All comments welcome.
I can resolve it. What do you think the map paths should be here? Since the feature isn't complete does it matter that they're pointing 1 directory up?