Add buildbot Makefile for CI.

* Configures Riak with both HTTP and PB, LevelDB backend.
* Runs the 'create_bucket_types' distutils command to create the
  appropriate bucket types.
* Lints using pep8 and pyflakes.
* Runs the entire suite with YZ enabled.

Note this requires basho/basho_buildbot#12.
Merge pull request #324 from basho/feature/sdc/buildbot

Add buildbot Makefile for CI.