Use the oracle-java7 parent from dockerfile.
Merge pull request #2 from mbruggmann/dockerfile-java

Use the oracle-java7 parent from dockerfile.
Specify the cassandra version we want to install.

It wouldn't build otherwise now that the newest package of
cassandra and dsc disagree.
Merge pull request #4 from mbruggmann/fix-cassandra-version

Specify the cassandra version we want to install.