Include Immutable Collections From Guava

It would be nice to have the Immutable Collections included with this library. https://github.com/google/guava/wiki/ImmutableCollectionsExplained

If it would be considered too large, maybe the different packages could be split up into sperate jars based on packages, to allow users to pick and choose the pieces they need. Sort of similar to how google play services works (except not as large).

Let me know what you think and if you need any help implementing this feature.