[Add]: `opCheckboxSet` and `opCheckbox` directives

Other changes:
- Adopt ngAnimate
- Add '.slide-show-hide' animation class (implemented in javascript)
- Add '.fade-show-hide' animation class (implemented in CSS)
[Mod]: Support for Reveal with UI Bootstrap modal

Originally, I made a custom change to UI Bootstrap modal to make it
support Foundation 4 Reveal. After taking a second look at this
feature, I use a decorator on the `$modal` sevice to make it support
Reveal while leaving the `$modal` service intact.