Support StickyListHeaders

Supporting StickyListHeaders for basic animations.

To use it:

    compile 'com.nhaarman.listviewanimations:lib-core-slh:3.0.0'

For now, a `-SNAPSHOT` is available.

Classes: `SLHAlphaInAnimationAdapter`, `SLHSwingBottomInAnimationAdapter`, etc.
The `AnimationAdapter`s need to be wrapped in the `StickyListHeadersAdapterDecorator`.