Implement shed_test command.

[jmchilton]

• Don't test local stuff - test stuff published to shed.
  • Setup an on-the-fly Galaxy instance with planemo.galaxy_config module.
  • Update to actually configure shed artifacts.
  • Use bioblend to install the repository.
  • Run the tests (I think run_tests.sh --installed might be do this).
• Allow specifying a shed_target.
• Use .shed.yml to resolve id, etc....

[peterjc]

When you say "Don't test local stuff - test stuff published to shed." I assuming this would catch mismatches between local files in the git repository vs the files actually included in the tar-ball which would be published on the Tool Shed (e.g. incomplete manifest information in .shed.yml)?