Add options for custom typeface and make recyclerview a provided dependency

[ZacSweers]

Two parts:

• Added options for setting custom typefaces for the snackbar text and action label, with an update to the sample app for this.
• Make RecyclerView a provided dependency.

To elaborate on the second part a bit (from the commit message):

If a developer doesn't use it, then this becomes an unnecessary extra dependency that exists for the sole purpose of attaching to and dismissing when a recyclerview scrolls. By marking it provided (and moving some code around), we can make sure this there for the developers that need it without unnecessarily burdening other developers with it as a transitive dependency.

I did the same thing for @afollestad's Material-Dialogs library as well a few weeks back. A library should be as lean as possible, and using provided allows for that flexibility. The only downside here is that you lose the compile-time type checking on the attachToRecyclerView method and instead have to have it at runtime.

[ZacSweers]

Here's a screenshot of the custom font setting in action

[wmora]

thanks!

[ZacSweers]

Happy to help :)