Update Snapshotter to work with Ruby 2.0.0

I forgot that we are supporting Ruby 2.0.0 alongside 2.1.0. This commit
fixes issues with 2.0.0 not supporting named required parameters without
a thing after the comma.

In 2.1.0 this is ok:
  def foo(name:)

The 2.0.0 equivalent:
  def foo(name: raise)