Mirror directory structure from`pyvows/assertions`  in `tests/assertions`
(Fix #67) A simple `__init__.py` fixed things ;)

“D’oh!”
`aptitude` → `apt-get` (for Travis)

Getting an "`aptitude not found`" error.  Odd…

Advised by support from Travis IRC channel to try `apt-get` instead.
Merge pull request #78 from Zearin/bug/67_error_on_reorganizing_vows

Fix #67: Error on reorganizing vows