Issue #23 - Memory Dump for Large RDB Files

Ability to quickly parse large files.
This is just a preview, I will need to cleanup still and test

Steps:

1) Generate a quick memory dump and index.  In quick mode, only compressed_size is valid.
rdb.py -c memory -q --file redis_memory_quick.csv redis.rdb

2) After viewing, dump a hash/list to view contents of a offending key
rdb.py -c memory --max 1 --pos 3568796958 --key mongow --file redis_memory_mongow.csv redis.rdb


Todo:
Cleanup the ziplists sizes
Fix other callbacks (only memorycallback works)
Regression Test