Tests now run without a ~/.exobrainrc file

- Added a Exobrain::Test scaffold
- Added an .exobrainrc to the test dir
- Updated dist.ini to not prune .exobrainrc in test dir
- Changed class names in t/payload_constructor.t

Huge thanks goes to @mmcclimon who did all the hard dist.ini
work in GH #23, which this commit steals from liberally. ;)