Fixed ModalOptions.windowClass having no effect

The Modal service did not pass the windowClass option to the ModalWindow component.
Merge pull request #106 from just95/patch-1

Fixed ModalOptions.windowClass having no effect
Fixed animation of modal backdrop

The backdrop is currently not animated because of a timing issue.
Added timeout to ModalWindow.attach

The action of setting ModalWindow.animate to true must be deferred by a few milliseconds such that the .in class is added after .fade.
Update modal.dart
Renamed animate to visible

Renaming animate is less confusing and makes its relation to .in more obvious.
Renamed ModalOptions.animate to preventAnimation

The name animate implied that the option enables animations, but it actually prevents them.
The default value was set to false.
Merge pull request #108 from just95/patch-2

Fixed animation of modal backdrop
Merge pull request #109 from just95/patch-3

Fixed modal animation
Added ModalOptions.size and ModalWindow.size

Allowed values are 'lg' (large) and 'sm' (small)
Added sizeClass to .modal-dialog
Added documentation of ModalOptions.size
Merge pull request #110 from just95/patch-4

Added support for optional modal size.
Added modal fade out animation.

ModalWindow.visible now uses ModalInstance._visible
ModalInstance._visible now controls the .in class of .modal instead of the display property of modal-window. 
Thus ng-class is no longer needed.
Removed ng-class

ng-class is not needed anymore because the .in class is now controlled by ModalInstance._visible
Merge pull request #111 from just95/patch-5

Added modal fade out animation
Prepare to Angular 1.0 migration