Added Client object, Users.company, Projects.client
fixed ``db.DBSession`` call examples in design.rst
fixed ``Status`` class documentation
removed unnecessary parameter in ``stalker.models.walk_hierarchy()`` docstring
started implementing ``create_alembic_table()`` to ``stalker.db`` module
Merge branch 'develop' of https://github.com/Industriromantik/stalker into Industriromantik-develop
updated User and Project classes, tests of them and the new alembic revision related to the new Client class
Merge branch 'Industriromantik-develop' into develop
0.2.8.a1
========

* **New:** Added a new class called ``Client`` which can be used to track down
  information about the clients of ``Projects``. Also added ``Project.client``
  and ``User.company`` attributes which are referencing a Client instance
  allowing to add clients as normal users.

* **New:** ``db.init()`` now creates ``alembic_version`` table and stamps the
  most recent version number to that table allowing newly initialized databases
  to be considered in head revision.

* **New:** Dropped ``mocker`` library from requirements list in setup.py, and
  replaced all the needed functionality with a simple patcher.
Added generic_text attribute to SimpleEntity
fixed code to pass all tests
Merge branch 'Industriromantik-develop' into develop
generic code cleanup toward py3k compatibility
removed unittest2 dependency
removed anything related to unicode
converted all **u""** style unicode string definitions to normal strings
removed all __eq__ methods in a try to pass tests under python 3
Stalker is now fully python 3 compatible
fixed str/unicode python 2 incompatibility
fixed a couple of issues about str/bytes/unicode/python2/python3 in Link and Version classes