TinkerPop 3.0 support

[amcp]

Upgrade use of traversal sources for TP3, other TP3 syntax
Use orient-gremlin until OrientDB is officially supported
Dependency version upgrades
Other small improvements

[sarovios]

Do we have any performance benchmarks between TP API and Neo4j native API?

[sarovios]

This is not related with this PR but I just find it out. I am not able to build the project, it seems that dynamoDBLocal is not on Maven Central as I get this: No versions available for com.amazonaws:DynamoDBLocal:jar:[1.10, 2.0.0). Please add the fix to README.md

[amcp]

I updated the README.md with some preliminary benchmark results. OrientDB is not officially at TP3 yet so I did not run these tests. I made some interesting findings especially with regards to how we were setting custom vertex ids in Titan. It turns out that our original implementation of custom vertex ids never worked. I found this out by enabling assertions (-ea) with the JVM and saw Titan core crap out in many places. I fixed the issues with setting custom ids in Titan, but I am not sure we stand to gain much from custom ids, so I will play around and see if using auto-ids improves performance.

[sarovios]

Shall I close that and create a new PR when this is ready?