Abstracted DateInput and added Key handlers

Supported keys:
- ArrowUp: increase date type (year/month/day)
- ArrowDown: decrease date type (year/month/day)
- Enter: close date-picker
Removed unneeded semicolon
Processed @markijbema's comments
Added JSHint to Grunt#watch
Merge pull request #35 from Hacker0x01/add-jshint-to-grunt-watch

Added JSHint to Grunt#watch
Merge pull request #34 from Hacker0x01/airplane/key-handlers

Abstracted DateInput and added Key handlers
Merge branch 'master' into upgrade-dependencies