Use boost::iostreams for compression streams

[constantinpape]

Boost iostreams already supports gzip and bzip2 and there exists an implementation for lz4. So this would solve most of #4.

This would mean getting rid of the CompressorClass and instead teamplating the stream (mixins pattern) into the ChunkIo.

However, I couldn't find a blsoc stream, so I would probably need to write this myself...

http://www.boost.org/doc/libs/1_65_1/libs/iostreams/doc/index.html https://github.com/zed-0xff/boost_lz4_filter/blob/master/lz4_filter.cpp

[constantinpape]

Not that this also supports platform independent memory mapping :). http://www.boost.org/doc/libs/1_65_1/libs/iostreams/doc/classes/mapped_file.html