added a test runner for running tests out of a setup.py file

Summary: I wrote this so we could use arcanist with projects like jar

Test Plan: none

Reviewers: tail, charles, jeff

Reviewed By: charles

CC: SamParker

Differential Revision: http://phabricator.local.disqus.net/D7473
Fix DDN for new transaciton interface
Update Arcanist API
Add generic XUnit test engine class.

Summary: This is necessary for the new Next repo and useful for other projects too.

Test Plan: N/A

Reviewers: dctrwatson

Reviewed By: dctrwatson

CC: benvinegar

Differential Revision: http://phabricator.local.disqus.net/D8248
Update .arcconfig boilerplate to have Jenkins config

Test Plan: N/A

Reviewers: dctrwatson

Reviewed By: dctrwatson

Differential Revision: http://phabricator.local.disqus.net/D8247
Don't force arc command to use libdisqus

Summary:
After D8242, we won't need to force `disquslib` in the `arc` command so remove that.

Depends on D8242

Test Plan: N/A

Reviewers: dctrwatson

Reviewed By: dctrwatson

Differential Revision: http://phabricator.local.disqus.net/D8249
Merge remote-tracking branch 'upstream/master'

Conflicts:
	bin/create-arcconfig