Update package and directory names

[mbrukman]

We need to do something similar to https://github.com/JanusGraph/janusgraph/pull/2/commits/0b6053375a94c7ab28f9ec4552e416783e4147d7 here, specifically:

• move files from com/experoinc/janusgraph → org/janusgraph
• update package names from com.experoinc.janusgraph → org.janusgraph

The links above point to the original cleanup commits in JanusGraph (coming from Titan), and may be useful for this cleanup.

However, before making these large-scale changes, it would be very handy to have a working .travis.yml config, so that these changes automatically tested.

[FlorianHockmann]

I think this is a duplicate of #10 for which we already have an open PR: #17. Although waiting for a Travis build probably still makes sense.

[mbrukman]

@FlorianHockmann — you're right, good catch!