Remove special-case for one ":" from PullCommand

This special treatment breaks images with registries with a port
specified, e.g. my-docker-registry:5000/my-namespace/my-image
Merge remote-tracking branch 'upstream/master'
Merge pull request #38 from hmrm/master

Remove special-case for one ":" from PullCommand
Port to Jersey/JAX-RS 2.0