Revert "Replaced callbackstream with node-concat-stream."

This reverts commit 15ef4c6b0e438e016a2d12fd1a7708ca2831d532.

Conflicts:
	index.js
Added navigator-based API. It has a gremlin style.
Added an example for the navigator api.
Added the Navigator.as operator to specify a var name.
Added Navigator.bind method to bind a specific variable to a value.
DRYed up the Navigator.arch* methods.
Added the ability to start the navigation from a variable.
Renamed Navigator.stream -> .valuesStream.
Adding the ability to return the contexts to the Navigator.
Testing the behavior of Navigator.contexts with no conditions.
Added the materialized API to db.join*
Added Navigator.triples* for returing triples.
Refactoring the triples and contexts support.
Added the Navigator.go method for changing the current vertex.
Added the Navigator API pull-request description to the README.
Merge pull request #4 from mcollina/navigator

Fluent API aka Navigator