Testing http refs
Reorganized project structure, fixed from_url issue with relative path to local file
Removed duplicate tests
simpler readme
Extracted (de)serialization stuff to separate file.
IDEA no longer complains.
ignored .idea directory
downgraded requests to 2.2.1 to match docker-py dependency
Removed 'parse_repository_tag' function as it now exists in the upstream docker library.
Support for fetching images that appear in a pipeline.

Runner interface now has `install_tool()` method that individual runners can implement.
JobNode and JobGraph now have install_tool and install_tools methods, that delegate to appropriate runner method.
CLI has install subcommand.
pep8 fix