Upgraded Grunt to 0.4

Started working on the code again and working with Grunt 0.3 was making me feel icky.

Highlights:
- I wasn't in the package.json list of maintainers, so I fixed that :smile: 
- The jshint options for Grunt were different to the ones in the .jshintrc. Unified them all and made Grunt load them from the .jshintrc
- Added testing on node 0.10 to the Travis config
- Source maps!
- Changed the default Grunt task to be just 'test' rather than the old default of 'generate the release files without testing anything' (?!)