feat($util): #933 - Add user-agent detector for IE11
fix($dnd): #933 - Fix IE11 exception

When dragging files from the OS filesystem into the browser's window
IE11 appears to prevent any access to the event's `dataTranfer.effectAllowed`
attribute. Even testing for its presence makes IE11 throw an `Unexpected call to method or property access`
so -- from my observations -- it's the browser blocking this here.

[1] - `effectAllowed` - https://developer.mozilla.org/En/DragDrop/DataTransfer#effectAllowed

comments
chore($SauceTests): closes #933 - Add IE11 to SauceLabs tests
fix($Gruntfile): Fix reference to renamed task