Uses the github.com/ghodss/yaml library to convert YAML to JSON before
unmarshaling for the purposes of supporting YAML and JSON input while
converting to only support JSON internally.

Bug: T207694
Change-Id: I00668014907e9ea54917f5d5067cac08d0668053

With the move to Gerrit and away from Phabricator/Arcanist, we lost an
easy way to run linters. New rules have been added to the `Makefile`,
`lint`, `unit`, and `test` that run linters, unit tests, and both
linters and unit tests, respectively.

Bug: T200452
Change-Id: I0742daaa14389841d88f13eba47dee07ac127cf2

Reviewers: dduvall, #release-engineering-team

Reviewed By: dduvall, #release-engineering-team

Tags: #release-engineering-team

Differential Revision: https://phabricator.wikimedia.org/D1059

Summary:
Refactored the Docker compiler to omit the stage name (`AS <stage>`)
from the `FROM` instruction when no dependent artifacts are declared.
This allows for use with older versions of Docker that don't support
multi-stage builds.

Test Plan: Run `go test` under the `docker` directory.

Reviewers: thcipriani, mobrovac, hashar, Jrbranaa, mmodell, #release-engineering-team

Reviewed By: mobrovac

Tags: #release-engineering-team

Differential Revision: https://phabricator.wikimedia.org/D684

Summary:
Now that the project is hosted on Phabricator the import URIs must be
changed.

Reviewers: thcipriani, hashar, Jrbranaa, mmodell, #release-engineering-team, demon

Reviewed By: #release-engineering-team, demon

Tags: #release-engineering-team

Differential Revision: https://phabricator.wikimedia.org/D657