added cancelled element to json, used taavis start/end props
added cancelled element to json, used taavis start/end props

pydata/symposion,toulibre/symposion,pinax/symposion,pyconau2017/symposion,euroscipy/symposion,toulibre/symposion,pyohio/symposion,pydata/symposion,faulteh/symposion,miurahr/symposion,miurahr/symposion,pinax/symposion,pyohio/symposion,faulteh/symposion,euroscipy/symposion,pyconau2017/symposion