Added the xz to the compressor ...

And changed the implementation so that we first format the entry and then write it using xz. Now i'm working on decompression to see what needs to be done
Merge branch 'master' of https://github.com/aghosn/persistence
Making progress in integrating the xz...

In our implementation. Still a glitch somewhere in the code, can't find it yet
Corrected a bug ...

Still one test failing though