Modified the timeout value semantics to better match the memcache cache backend, i.e. negative timeouts are instant expiration, 0 timeout is no expiration, and greater than 0 is time to live.

Bumped to version 0.9.0 -- Added ability to specifiy the parser class and the ability to use Unix domain sockets

Added the ability to use tcp sockets or unix domain sockets. Also added the
ability to specify a parser to use when processing responses from the redis
server.  To do this I had to bring back the custom connection pool, since
you need to instantiate a custom connection pool to be able to specify a
parser class.

Nudged to version 0.8.2.  Addresses handling of integers when using the 'get_many' method.  Fixes issue #20 on github.

Nudged to version 0.8.1, added ability to pickle the cache class. Added James Aylett to authors file.

Make cache object picklable.

To do this, we need to keep integers untouched while pickling any other type
of value. Existing tests should prove that the native incr is working, but
I added a test to show that if an integer was pickled and native incr is used,
then the cache backend will convert the pickled integer correctly.

The are two reasons:
* django already implements CacheClass instance as singleton, we don't
need to reimplement that
* connection pool in redis.py is already tested, we shouldn't have to
test it again
* default keywargs charset='utf-8' and errors='strict' are defaults in
redis.py, se we don't need to copy it over

Users should handle django.core.exceptions.ImproperlyConfigured better
then a custom exception with the same name

Since redis 2.1 EXPIRE command should not return false if key exists

Django is using timeout=0 to use default timeout value.

Using timeout=0 to set non-volatile keys conflicts with django API.

Let's raise exceptions when provided bad db and port values. Also Fixed tests and bumped version.  Thanks to Lior Sion

Created connection pool that lives across requests so that we can reuse connections.  Removed close method, since we don't want to close connections at the end of a request.