per-user command history

make sure that command history is tracked separately per every user that
talks to the bot
[ChatRoom] become Python 3 compatible

thanks to  https://github.com/oxplot/fysom/issues/1
which in turn references http://www.rfk.id.au/blog/entry/preparing-pyenchant-for-python-3/
HIDE_RESTRICTED_COMMANDS option added

if set to True in config will prevent restricted commands to appear in the help response
Merge branch 'tests' into pproduct
Add test for per-user command history
Merge branch 'master' into pr/120

Conflicts:
	errbot/builtins/chatRoom.py
Merge branch 'p120-unittests' into pr/120
Fix a python3 incompat. where bytes were concat'ed to strings.
Fix bot not recognizing commands in a chat if prefix is optional
Merge pull request #129 from arrrrr/master

Git repo handling breaks with python 3
Merge pull request #127 from gbin/per-user-command-history

Per user command history (merged pull requests from zoni and p-product contribs)
Merge pull request #130 from arrrrr/optional_prefix

Optional, but still working bot prefix on chat