django-redis-cache for django 1.3 (not compatible with 1.2 : new parameters to methods in BaseCache)

Thanks to Kami for the report and Jezdez for being awesome.

CACHE_BACKEND = 'redis_cache.cache://127.0.0.1:6379?db=2'

- Got rid of _prepare_key and _prepare_value
- Started using the base64 module directly
- Use the highest pickle protocol available
- Added a set_many method
- Added a delete_many method
- Added an expire method
- Made get_many return a dictionary as required

Got rid of the incr and decr implementation since we can't really increment/decrement the base64'd values.

Fixed a default timeout problem - if no timeout was specified the default timeout specified in settings was not used.

Now, you have three choices:
1. no timeout is specified - the default timeout is used
2. timeout is specified and it's not False - the specified value is used
3. timeout is specified as False - no timeout is set for this key and it does not expire