Moved to SBT and Neo4j v1.9.M04
Added a null check to Neo4jWrapper._toCCPossible that causes it to
return None now if the parameter is null.

Previously, a null would cause a NPE.

Also added a unit test for this.
Now all neo4j dependencies use version 1.9.1, except neo4j-rest-graphdb
for which the 1.9.1 version is not found in the repositories.
Completely removed the REST wrapping capability, including its
dependency in the sbt build file and its unit tests.
specify sbt.version for consistent builds
bumped scala.version
bumped neo4j version to 1.9.3