Script tests tied to interpreter

Command paths like:

  def default_command_path
    %Q{ruby #{LOAD_PATHS} "#{RAP_EXECUTABLE_PATH}"}
  end

Have the effect of tying a script test to a particular ruby interpreter... not what you want. The interpreter may need to be determined dynamically, or, maybe a whole new solution is needed. After all, this presupposes a developer calls 'ruby' in the first place.

Currently affects (in tap):

• generator_test
• run_test
• tap_test
• readme_test