Post recycling gif frame resources.

Hack for #219
Do a get before put when pre filling.

Otherwise it's likely our new Bitmaps will be 
immediately evicted.
Obey default DecodeFormat in prefill API.

Also does some cleanup, including switching to use
a builder and re-naming a few classes.
Pull disk cache forward.

Fixes #222
Use sample size to acquire Bitmaps in Downsampler.

Fixes #224
Avoid expanding buffer to fit entire image.

Fixes #225.
Add a back off to bitmap pool pre filling.
Set fixed dependency versions using properties.
Fix missing Config warnings.
Move TestUtil in gif decoder into test package.
Explicitly set JUnit4 runner for junit tests.
Avoid I/O in DecodeJobTest
Add jacoco coverage report.
Make AnimationFactorys top level and add tests.
Fix checkstyle config in Intellij
Fix some holes exposed by coverage report.
Replace Hamcrest with Truth.

Fewer static imports, better wrangling of generics
(particularly when asserting contains), and, least
of all, better internal support.
Avoid static references to android classes in test

Depending on the order tests are run in, this
seems to be able to cause errors.
Remove duplicate test class.
Revert "Avoid expanding buffer to fit entire image."

This reverts commit deef4ae2607fcbd32caffc03e2490cbca9134643.
Fixes #231.
Reopens #225.