adapt to changes in AndroidAsync performed to fix issue 461

[mkoslacz]

I performed changes to adapt this library to work on top of AndroidAsync modified by me in commit koush/AndroidAsync@98a9d50.
It's rather quick fix, using not the best patterns, to get the stuff done, but it works flawlessly. Probably you will want to adjust it to meet your standards.
I used FileCache named storeCache in Ion to resolve method calls that were static, and I changed Ion reference to static in IonBitmapRequestBuilder, assuming that Ion is anywany called in static way, to prevent changing other methods to non-static.

[koush]

Ion is not always called in a static way. There may be different ion instances with different configurations, middleware, etc.

[koush]

I think you want to use getResposneCacheMiddleware().getCache() instead of the store cache.

The store cache is an experimental/undocumented thing to do disk i/o

[mkoslacz]

I'll take a look later. If it's not always called in a static way, static methods in IonBitmapRequestBuilder will probably need to be changed to non-static, which can cause need for further changes. Although, in my simple use case it works good.