add initial impl of lz4 compressor

This is an initial implementation of LZ4 support. This is inspired by what is done on https://github.com/datastax/java-driver or https://github.com/ning/jvm-compressor-benchmark with regards to optimisations for decompression. 

related to #12 

I added a fairly simple test, it "seems" to be working with stress-data but I didn't dig deeper as it is a bit late here already :)