clever-specific changes to Heka

Branched off of 0.5.2, current stable release
  1. Include Vagrant for development (a lot of us use OS X)
  2. Cherry-pick https://github.com/Clever/heka/commit/53079a811d11dd760b25ee1a574e1768e5e86fee, or the tests won't pass in go 1.3
  3. Add a tweak version that we can increment
  4. Compile with mozsvc plugins, for sentry output

TODO: Write a sphinx decoder plugin, probably in it's own separate repo, and include that plugin here.