Let the user choose which reveal animation to run

[Mauker1]

As of version 1.2.2, if we choose to animate the search view when we're opening it, the animation type is decided based on the API level. If the device is running a pre-lollipop android, it'll use fade-in and fade-out, for api 21+ it'll use circular reveal.

It might be interesting to let the user choose what kind of animation should be used, if any.

Possible problems:

• CircularReveal won't work on pre-lollipop. Unless we get the animation from a third party lib, but it'll just make MSV bigger.
• Should we add custom animations? If so, we should also consider a "custom" animation type.