Revert changes from upstream repository to build the java-koans with Docker because they appear to only support building the master branch.  That is, Travis could no longer build against a pull request.
Revert changes from upstream repository to build the java-koans with Docker because they appear to only support building the master branch.  That is, Travis could no longer build against a pull request.

DavidWhitlock/java-koans,DavidWhitlock/java-koans