* Pass `**kwargs` to backend storage classes, split out any that are valid for the backend-specific connection function/class, and pass them to the connection * Add intersphinx links to docs for dependencies * Update and format some more backend class docstrings * Remove 'Unrecognized keyword arguments' warning from `BaseStorage` * Turn `warnings.warn` about using secret keys into a `logging.warning` (due to complaints about too many messages)
* Also allow passing a backend class (in addition to backend name and instance) * Detect duplicate params: Backends have different keyword args equivalent to the `cache_name` positional arg, for example `db_name`. If one of these is passed as a keyword arg, it results in a `TypeError` due to duplicate args (See #94). * For backends without dependencies installed, use a placeholder class to delay and re-raise the original `ImportError` * Add type annotations