Speed up Grunt a bit, especially JS compilation with --dev

running `grunt compile:js --dev`:

before
![screen shot 2014-08-13 at 14 51 17](https://cloud.githubusercontent.com/assets/867233/3906351/2eb99988-22f2-11e4-8a87-6f2d6266ffce.png)

after
![screen shot 2014-08-13 at 14 50 34](https://cloud.githubusercontent.com/assets/867233/3906329/0f58f6c4-22f2-11e4-9f9b-8c5765194cac.png)

@ironsidevsquincy @mattosborn @phamann i’m aware there’s a lot going on the grunt file, and I may well have missed a good reason for optimize being on by default in requirejs - is this ok?