bugfix:  set multiple response on a job
remove unused ParallelByCommandOperation
move event dispatching to operation_base
allow query string params in event urls
call failure response_link on job failure
duplicate petri mixin for command
support multiple sequential methods

This is a general kind of "shortcut" approach, where the first method to
succeed in a list of methods will be considered to have generated the
outputs for the command.
add a test of shortcut succeeding
Merge pull request #5 from mark-burnett/add-shortcut

Add support for shortcutting