Remove the old setup_py command.

It has been replaced by the python_setup goal.

There are no longer any remaining commands in pants, other than GoalRunner.

Note that this requires 49bb9f43eeb1331342f35cef331265cf4b8199bb, so it may not work if you cherry-pick it.

Testing Done:
CI passes.

Reviewed at https://rbcommons.com/s/twitter/r/1448/
Move the spec exclude integration test from command to base.

It is base-level functionality that has nothing to do with command.

Testing Done:
Integration test passed in its new location.

CI baking.

Reviewed at https://rbcommons.com/s/twitter/r/1449/
migrate_config only complain about keys not from defaults

has_option seems to return true if a key is found from defaults even if it isn't overridden
in a given section (ours was complaining about 'confs' in a a mostly empty junit-run section).

This seems to fix it, though in the event a section was actually overriding a default,
just with the same value, it will ignore that. I couldn't figure out how to see if a section
actually defined a key without poking around in ConfigParser's private fields.

Reviewed at https://rbcommons.com/s/twitter/r/1451/