Allow on_start hook to use exe and args instead of command.
Allow on_start hook to use exe and args instead of command.

johanneswuerbach/testem,fotinakis/testem,bradleylandis/testem,testem/testem,fotinakis/testem,testem/testem,Addepar/testem,testem/testem,Addepar/testem,paulot/testem,paulot/testem,johanneswuerbach/testem,Addepar/testem,fotinakis/testem,johanneswuerbach/testem,Addepar/testem,bradleylandis/testem,paulot/testem,bradleylandis/testem