Allow returning a Bitmap instance directly from the loader.

This support fun use-cases like allowing Base64-encoded images inside JSON or rendering a dynamic image based on the response data.
Merge pull request #167 from square/jw/direct-bitmap

Allow returning a Bitmap instance directly from the loader.
Request data and transformer API
Fix get() and fetch() request keys.
Javadoc for request transformer.
Merge pull request #168 from square/jw/request-data

Request data and transformer API
Hook up stats again
Merge pull request #188 from square/dimitris/stats-again

Hook up stats again
Add module which uses Pollexor to rewrite requests for Thumbor.
Fix tests
Merge pull request #191 from square/jw/pollexor-transformer

Add module which uses Pollexor to rewrite requests for Thumbor.
Use long instead of int for max cache size.
Merge pull request #192 from square/dimitris/long-size

Use long instead of int for max cache size.
Better retrying for NBH.
Fix debug indicator.
Merge pull request #194 from square/dimitris/debug-indicator-fi

Fix debug indicator.
Merge pull request #195 from square/dimitris/retry

Better retrying.
Prepare for 2.0
Merge pull request #196 from square/dimitris/change-log

Prepare for 2.0
Fix checkstyle.