Retour à pexpect

pexpect-u avait été créé parce que pexpect n'était plus maintentu, mais
ça n'est plus le cas maintenant. On peut revenir sur pexpect > v3.0.
Removed sflvault-common reference from --version listing
Fixed tests which were broken
Replaced sflakes with tox

Also, added flake checks (previously, there were only pep8 checks) as
well as line length checks (130, otherwise, there's too many corrections
to make at once).
Moved server/sflvault/tests to test/server

Also, added tox.ini which was not added in previous commit because it
was shadowed in the .gitignored

Tests are now fully runnable through a simple "tox" invocation.

Removed coverage because its usage was rotten. We'll re-add it properly
later.
Make tox fail when one of the tests fail
Merge branch 'develop' into build-refactor

Conflicts:
	client/setup.py