module CompassRails

def set_maybe(sass_config, compass_config, sass_option, compass_option)

has been explicitly set by the user.
sets the sass config value only if the corresponding compass-based setting 
def set_maybe(sass_config, compass_config, sass_option, compass_option)
  if compass_value = compass_config.send(:"#{compass_option}_without_default")
    sass_config.send(:"#{sass_option}=", compass_value)
  end
end