Added support for using remote Redis instances

The previous version worked fine with a local Redis instance running on the default port/db, but there was no obvious way to specify a remote Redis instance of use non-default parameters.  This patch is fully backwards-compatible, but allows users to pass a HotClient instance (with any Redis connection parameters) to HOT Redis types using the "client" keyword.  A .gitignore file has been added to mirror the .hgignore.  Documentation has also been updated for the patch.