alchemy.get.allNodes() can take nodeType as an arg
alchemy.get.allNodes() can take nodeType as an arg

Fixes #359
The issue itself references it as alchemy.allNodes() but I moved it to
alchemy.get.allNodes() for consistency's sake.

GraphAlchemist/Alchemy,mayblue9/Alchemy,kylerob/Alchemy,jimtom2713/Alchemy,jimtom2713/Alchemy,kylerob/Alchemy,mayblue9/Alchemy