App/Cluster configuration using URL

[jirikuncar]

Add support for App/Cluster configuration using URL.

-- see also http://docs.sqlalchemy.org/en/latest/core/engines.html#sqlalchemy.engine.url.URL

[davebshow]

I don't necessarily feel very strongly about this either way. What is your reasoning behind the feature? Why do we need it? Why is it better? Is it worth moving away from the pattern established by the Java driver? Etc. Etc. Etc. Also, maybe this is something that may be better addressed in aiogremlin.

[jirikuncar]

It's easier to provide single environment variable instead of separate host, port, username, password, etc.

[davebshow]

Yeah that would be nice, config files suck anyway. +1 go for it.