Working compressor and decompressor

- Working compressor
- Working decompressor
- Store all compressed data in a file
- Addition of tests for (de)compression

TODOS:
- Optimize the compression (stil slow).
- See if we can have a better compression by modifying a bit the way the
compression dictionary is generated.
- All the rest.
Merge branch 'master' of https://github.com/mdemarne/persistence