Implement ConstantPartitioner
Use the ConstantPartitioner in the functional test
Merge pull request #160 from Shopify/constant-partitioner

Implement ConstantPartitioner
Add Vagrantfile, and provisioning scripts that set up a working 5-node cluster.

The provisioning scripts are also used on Travis CI.
Re-enable go 1.2 and go 1.1 on Travis
Merge pull request #161 from Shopify/vagrant

Add Vagrantfile, and provisioning scripts that set up a working 5-node cluster
New Producer design
Make channels between topicDispatcher and partitionDispatcher, and partitionDispatcher and leaderDispatcher buffered
Fix shutdown process

- make Close() wait til everything is cleaned up
- fix to avoid sending on closed channel in certain cases

Also: make the "metadata overhead" byte count exact in byteSize().