This commit adds support for build release artifacts and
publishing them. Currently we support binaries that are published
to github release, docker containers that go to hub.docker.com,
and rkt ACIs (which are not currently published).
Makefile now checks go dependencies and only builds what is needed.
Refactored the Makefile into three parts for better maintenance.
Add a buildall target that is the initial attempt at cross compiling
castlectl.
Bassam Tabbara
Travis Nielsen
Bassam Tabbara