Create cloud volume

[ceesem]

While cloudvolume should not be a requirement, making a cloudvolume instance from a client is a frequent task with a good bit of boilerplate and some options that always require explaining to new users. This aims to add a convenience function in the client that provides sensible defaults.

[fcollman]

to simplify install we might want to add a optional requirement to the setup.py

[fcollman]

so we can install it with pip install caveclient[cloud-volume]

[ceesem]

so we can install it with pip install caveclient[cloud-volume]

I like this idea. It's almost always useful if you're doing analysis, but also nice to avoid for lighter services.