Split library

Splits library in `lib-core` and `lib-manipulation`.
Basically, everything in package `com.nhaarman.listviewanimations.itemmanipulation` has moved to `lib-manipulation`.

Libraries can be accessed like this:

    compile 'com.nhaarman.listviewanimations:lib-core:3.0.0'
    compile 'com.nhaarman.listviewanimations:lib-manipulation:3.0.0'

`lib-manipulation` requires `lib-core` to be present.
For now, `-SNAPSHOT` releases are present.

Fixes #190