volumes parameter on container_create should be validated

[discordianfish]

If you create a container like this:

client.create_container("busybox", command="true", volumes="/data", name="test-data")

It won't create volumes since docker-py passes volumes, as given to the function, as a string to the docker api.

Instead it should either raise a exception if the user passes a string as 'volumes' or even better convert it to a dict before passing to the api.

[beneshed]

+1

[shin-]

Fixed by #291