Chase the bugs

Minor changes from 2.0.0

• TVS codes are trimmed to the first word available (PNO PNO_TRANS returns PNO as a TVS code)

• #departure and #arrival methods on the Train object returns Station objects without doing any call to sncf.com when called from #departing_trains or #arriving_trains from a Station.

  E.g.

  > Station.find_by_sncf_id("frlpd").departing_trains.first.departure
  => <#Station name="Lyon Part-Dieu" ..>
  

  Instead of

  > Station.find_by_sncf_id("frlpd").departing_trains.first.departure
  (... HTTP Request to sncf.com ...)
  => <#TrainStop station=<#Station name="Lyon Part-Dieu" ..> ..>