Various and sundry fixes

Fixes for bugs uncovered by @bbangert's [tester](https://github.com/bbangert/push-tester) and my [Go port](https://github.com/kitcambridge/push-tester-go), along with a Heka logging refactor.
`gpm` and `go get` will stomp on one another when downloading packages from the same repo: `go get` runs `git pull --ff-only`, which fails if `gpm` checked out a specific revision.

Currently, `gpm` runs `go get` and `git checkout` for all dependencies in parallel; we can either modify `gpm` to download in parallel and then run `git checkout` (ensuring the versions match for packages from the same repo), or vendor everything.