This adds the ability to build a tar output image. The /compose and
/compose/types API routes are now available.
To start a build POST a JSON body to /compose, like this:
{"recipe_name":"glusterfs", "compose_type":"tar", "branch":"master"}
This will return a unique build id:
{
"build_id": "4d13abb6-aa4e-4c80-a671-0b867e6e77f6",
"status": true
}
which will be used to keep track of the build status (routes for this
do not exist yet).
