Remove Rexster batch kibble dependency
Give Gremlin instances (instead of gRex instances) the responsibility to return Graph instances

- give Graph methods the responsibility to prepend g. to the Gremlin
script string when called
- add Gremlin.subScript() method
- each Graph instance now has its own distinct Gremlin instance to
append some Gremlin script strings to
Allow optional naming of a Gremlin instance graph getter
Remove a console.log() in test
Add ArgumentHandler.handleArray() method
Extract ArgumentHandler.stringify() method
Rename gremlinsteps.js test file to pipeline.js
Update .select() tests description
Add more descriptions for pipeline tests
Move Graph and Element tests away from Pipeline tests to their appropriate files
Add a Pipeline.key() gRex specific method to allow chaining of arbitrary property names

This may change with ES6 proxies / anonymous getters
Add test for .exhaustMerge()