Version 0.7.29

+ improvements in db module:
  * added new Tariff class to use in payment system.
  * implemented basic payment system for fixed tariffs
    via TariffPayment TariffExcessPayment.
+ major improvements in payments module:
  * BARReader -> Reader
    This class now handler all aspects of asynchronous
    input and payment processing in a separate thread.
    Additionally it also handles periodical tariff updating.
  * Payments class now implements fully asynchronous handling
    of ticket payments using Reader class as reactor.
  * Pyaments user interface has been improved to usable state.
+ mainloop.Mainloop now longer tries to instantiate DB object with itself as parent.