Issue 372: Add support for 'bikes_allowed' fields

Add support for proposed "bikes_allowed" field in GTFS routes.txt
and trips.txt files.  See disscussion at:
  https://groups.google.com/d/msg/gtfs-changes/rEiSeKNc4cs/gTTnQ_yXtPgJ


git-svn-id: http://googletransitdatafeed.googlecode.com/svn/trunk@1819 705c8f7f-ad29-0410-9695-93dd3b14b492