Refactor

IMPORTANT: This will require updating Docker Hub after merging into master.

This is a refactor that does a number of things:
 1. Consolidates branches into one branch with multiple sub-image projects
 1. Adds mechanism to pull changes upstream from Heroku's cedar-14.sh
 1. Produces tar and tar.gz of cedar14 filesystem as *versioned* releases
 1. Uses CircleCI for building those releases and soon testing

However, the Dockerfiles remain unchanged, so this should not effect the Docker Hub images ... as long as the automated build definitions are updated to the new paths. The plan is to later switch Dockerfiles to just adding the versioned filesystem tar on top of scratch. This allows the latest tested images to be used via Docker Hub as usual, but also allows advanced builders to optionally download and import specific releases directly for more efficiency and control.

My question before merging is ... how can we efficiently test cedarish? At least a smoke screen test ... more in-depth buildpack and app testing will be done at a higher level (in another project).

Also, there is a bug preventing locales to be generated from containers on CircleCI. It's been reported and until fixed, maybe we should hold off merging?
can we add a `make deps` target for installing `gh-release`?