Remove boolean returns from `mouseMoveEventHandler`, fixes #190. Add limit_to_screen check within `_isWithinBoundsX`, fixes #204. Add item existence check to `_dragStart`, fixes #208.
Remove boolean returns from `mouseMoveEventHandler`, fixes #190.
Add limit_to_screen check within `_isWithinBoundsX`, fixes #204.
Add item existence check to `_dragStart`, fixes #208.

BTMorton/angular2-grid,BTMorton/angular2-grid,BTMorton/angular2-grid