Adds id to Galactic.Node attributes.
Galactic.Node instantiation error checking now includes id.
Updates specs to for addition of Galactic.Node ids.
Reverses argument order in Galactic.Node.random.
Use Galactic.Node.id as refernence when adding Galactic.Graph edges.
"Updates Readme information on node data type to include node ids.
Adds error checking for Galactic.Node.id.
Galactic.Graph#addNodes increments node id...

of new nodes, if graph already contains nodes.
Adds Galactic.Graph#removeNodes, and correctly increments nodes...

when adding nodes to a graph that already contains nodes.
Adds test for Galactic.Graph#addNodes.