Migrate checkstyle's use of self.config to self.get_options() for fetching from pants.ini.

The options names should be backwards compatible.  However, the task doesn't seem to be wired in to any
goal at the moment, so I can't add a section name to the migration script.

Testing Done:
CI passed.

Bugs closed: 828

Reviewed at https://rbcommons.com/s/twitter/r/1399/
Allow setting the cwd for goals run.jvm and test.junit

Testing Done:
Added new integration tests
CI passed at https://travis-ci.org/pantsbuild/pants/builds/41324560

Bugs closed: 797

Reviewed at https://rbcommons.com/s/twitter/r/1344/
Switch pants's release and ci processes to the new setup-py goal.

Testing Done:
ci.sh passed.
Dry run of release.sh passed.

Reviewed at https://rbcommons.com/s/twitter/r/1402/
doc: what a command line looks like nowadays

Reviewed at https://rbcommons.com/s/twitter/r/1370/
tech talk prezo: Pants Essentials. Excellent feedback is excellent

Reviewed at https://rbcommons.com/s/twitter/r/1407/
Exit workers on sigint rather than ignore