Travis, Grunt, more options and improvements

- Added travis CI build support to jshint any code
- Trak() renamed to trak() to avoid confusion
- Added more options:
 - `trak.clean` is now optional
 - `trak.options.additionalTypes` allows custom event tracking to be used
 - Google Tag Manager can be specified in the options, value should be `gtm`
 - Set `trak.options.debug` to true to see debug logs
- No longer include our own domready listener to call trak()
- Grunt build tasks added to help development