use pytest instead of nose
Fix docs and CI script (use py.test)
Fix doctests

Use generator based test case behavior (this should work in pytest as
well as in nose) instead of `DocFileSuite` quirk, as the latter doesn't
work with pytest.

This is a bit of a hack (though not uglier then before) and should be
replaced by proper pytest doctest support.
Store session values in cookies.

Currently, we (or more precisely, beaker)  store session values in the filesystem.
That does not scale, and is extremely hard to synchronize across multiple machines.
Therefore, this code adds a new flag adhocracy.session.implementation that can be set to "cookie" to use a new session implementation which stores the session data in cookies.
The current implementation does not encrypt the stored data (as I haven't found any secret values), but does check a signature in order to prevent users from meddling with these values.
PEP8 improvements
Check for empty keys as well
Only use a single cookie for session data
Check session expiry in cookie-based sessions
Default session lifetime to an integer

If a year seems overly long, consider that github uses 10 years.
Clean up cookie session implementation
Correct setting and deleting of cookies
Ignore Pylons-related deprecation warnings in test suite output
Cleanup tests/__init__.py - remove pylons-0.9 traces
Fix user import doctest

This was broken as Adhocracy doesn't return a 401 unauthorized response,
but is automatically redirected to the login page. The test now checks
for the latter.
Minor cleanup in test.ini.in
Allow to disable tutorials installation-wide (fixes #54)
Move FriendlyFormPlugin into adhocracy code (Preparation for #352 and general improvement of the login form)
Centralize login form rendering
Simply default having a password in the alternate login form (Fixes adhocracy.hhu_theme#289)
Alternate login form: Move input out of label (Fixes hhucn/adhocracy.hhu_theme#289)