Version bumped to 2.0.0-beta-6 (work in progress)

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>
Work on compression:
 - BZIP2Compressor now based on Commons Compress (performs better than jbzip2 and this means we can drop the in-project repo)+
 - support for headerless BZIP2 (saves 3 bytes)
 - All Compressor implementations now expose OutputStream/InputStreams
 - Major clean-up of LZMACompressor code
 - Tweaking of dictionary size on LZMACompressor & LZMA2Compressor to avoid excessive memory usage

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>
Some warnings killed

Signed-off-by: Matthias Stevens <matthias.stevens@gmail.com>