Merge pull request #835 from stevvooe/next-generation

Lock down HTTP API error codes
Re-enables "go vet" in circle.yml
Merge pull request #838 from BrianBland/ng-circle

Re-enables "go vet" in circle.yml
Merge pull request #839 from stevvooe/next-generation

Initial Dockerfile for running registry
Export error descriptors and provide tool generate markdown table

To support accurate specification generation, this changeset includes a quick
and dirty tool to generate a markdown table of error codes generated by the
registry API. Equivalent supports for routes will likely follow.

Exported descriptors could be used to generate other documentation, as well.