Patch the connection instances.

This patches the connection object (which is either a StrictRedis
instance or a Redis instance), to have alternative class methods that
behave exactly like their StrictRedis counterparts, no matter whether
which type the object is.  Only the ambiguous methods are patched.  The
exhaustive list:

- _zadd          (fixes argument order)
- _lrem          (fixes argument order)
- _setex         (fixes argument order)
- _pipeline      (always returns a StrictPipeline)
- _ttl           (fixes return value)
- _pttl          (fixes return value)

This makes it possible to call the methods reliably without polluting
the RQ code any further.
Merge pull request #3 from nvie/scheduler-integration

Patch ``connection`` to make it compatible with both ``Redis`` and ``StrictRedis``. Thanks @nvie!