Corrected the LoopTimer class to support both Python 2 and 3

Python 2: _Timer class
Python 3: Timer class
=> The class to use is the type of the result of Timer(...)
Wait for rooms to be created before inviting clients

The MonitorBot know waits for all requested rooms to be created (or to
return an error) before sending its invitations to the client.
LoopTimer does not inherit from Timer anymore

Avoids a not-so-readable type() trick and allows pylint to work
correctly
Added some comments to disable pylint on some compatibility tricks
Added pylint configuration

Same as in Pelix/iPOPO