Part two of client work.

Adds functions for submitting commands to a node, and getting a list of nodes from the system.

Open questions:

1. Right now the types are all of type 'string', should we alias these to something like 'Command' ?

2. Should the client maintain a list of valid nodes which may be sent commands based on the last run of the list node function?
(minor and not a blocker) There are a number of places where we need to form these paths, it maybe better to move them all to a ```m_etcd/paths.go``` file and make them a package func for m_etcd.