Runner should execute a built Scenario
Allow writing scenarios to tempfiles

This will be used later in runner instead of compiling to a permanent location.
Execute scenarios using tempfiles rather than permanent locations on disk
Sensible testing of Tempfile removal where it can be guaranteed

Conflicts:
	spec/sippy_cup/scenario_spec.rb
Add a ducktype of Scenario for running SIPp scenarios directly
Get all options to modify the SIPp command executed from the Scenario