added traffic plugin

* plugin is intended to serve traffic info about bus and train
  departures

Signed-off-by: Adrian Matejov <a.matejov@centrum.sk>
initial

Signed-off-by: Adrian Matejov <a.matejov@centrum.sk>
paramaters in get methon

Signed-off-by: Adrian Matejov <a.matejov@centrum.sk>