Build: Migrate to grunt 0.4.

Rename to Gruntfile, upgrade to newer grunt-css and grunt-html, update custom tasks. Drop qunit-junit plugin, not worth the trouble. Update release script to run grunt-prepare after npm-install.

tree diff between old and new dist:

```
1c1
< dist
---
> dist-0-3/
22d21
< │   ├── Gruntfile.js
270a270
> │   ├── grunt.js
```

File diff (`diff -r -w -q dist dist-0-3/`): https://gist.github.com/fb016517fa530ca75213

The banner creation changed: Whitespace is now more consistent, but slightly different. The "Includes: jquery.ui.[component]" line from non-concat files is gone.

Minifiers changed: grunt-contrib-uglify uses uglify2, grunt-css uses clean-css (instead of squish), so all minified files are different as well.

I've dropped the qunit-junit plugin instead of replacing it with the 0.4 compatible grunt-qunit-junit since that doesn't really work yet and the junit reports have provided no value to us while we were using 

I'm done here, but would like someone to review and test before a merge to master.