The new dep experiment (pending merger into the go toolchain with go

1.10) allows us to generate a lockfile à la npm or cargo so that we can

pin our dependencies. This also allows us to specify branches for said

dependencies, so we can use the upstream libgit2/git2go repository

pinned at branch v24 instead of relying on the gopkg.in service.

Built rb-gateway with dep.

Ran unit tests.