Stop allocating array lists for each hunter.

@JakeWharton 

This felt like it should be simpler.

The benefit is pretty good.

Most `BitmapHunter`s do not need to allocate an `ArrayList`. This further reduces unnecessary  object allocation for nothing.

With the various performance improvements the sample app runs pretty smooth almost always below the 16ms line.

![device-2014-02-10-194256](https://f.cloud.github.com/assets/310370/2133914/824edf06-92d1-11e3-9745-eedf3acd3f75.png)