AudioTrack will mark 0-size buffers as consumed

This can happen in the first, non-codec-config output buffer
from MediaCodec, while decoding MP3 data.

This issue was discovered on Nexus 5's running both KitKat
Lollippop.
Merge pull request #208 from alexandrite/fix-mp3-buffer

AudioTrack will mark 0-size buffers as consumed
Minor cleanup of AudioTrack.
Don't request that the server use DEFLATE compression.

If the server actually gives us a DEFLATE response, we
fail to handle it properly!
Merge branch 'dev' of https://github.com/google/ExoPlayer into dev
Merge pull request #211 from google/dev

dev -> dev-hls