Pass the default worker connection into the started and finished registries

In practice all the registry methods are called with pipelines, but if no
connection is passed in when instantiating the registry and the connection
stack is empty resolve_connection will raise NoRedisConnectionException.
allow depends_on to be a job id or a job itself

Other parts of the code (i.e.: the `.create()` method) allow the `depends_on` kwarg to be a `Job` object *or* a job id. This is an attempt to allow that same idea within the `.enqueue_call()` method for a queue. Since this part of the code requires actually knowing the precise redis key for the job that's depended on, my intuition is that a `.fetch()` is the only way to solve this.
use internal job_class for check
add PyCharm .idea folder to .gitignore
test for id based job dependancies