Clever-specific Heka release, with additional plugins

Branched off of 0.5.2, current stable release
  1. Include Vagrant for development (a lot of us use OS X, and Heka won't build with clang instead of gcc)
  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, in it's own separate repo, and include that plugin here via http://hekad.readthedocs.org/en/latest/installing.html#building-hekad-with-external-plugins
TODO: Add configuration to send Sphinx errors to Sentry