Spike: filter out stack traces from Ruby processes

[mefellows]

See the below example, most of the output is noise:

		  2) Verifying a pact between API and Metrics A request to create a metric with POST /metrics returns a response which has a matching body
		     Failure/Error: expect(response_body).to match_term expected_response_body, diff_options
		       Actual: 404 page not found


		       @@ -1,7 +1,2 @@
		       -{
		       -  "sent": {
		       -    "json_class": "Pact::SomethingLike",
		       -    "contents": true
		       -  }
		       -}
		       +404 page not found

		       Key: - means "expected, but was not found".
		            + means "actual, should not be found".
		            Values where the expected matches the actual are not shown.
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-expectations-2.99.2/lib/rspec/expectations/fail_with.rb:32:in `fail_with'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-expectations-2.99.2/lib/rspec/expectations/handler.rb:40:in `handle_matcher'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-expectations-2.99.2/lib/rspec/expectations/expectation_target.rb:59:in `to'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/pact-1.9.1/lib/pact/provider/rspec.rb:138:in `block (2 levels) in describe_response'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-core-2.99.2/lib/rspec/core/extensions/instance_eval_with_args.rb:16:in `instance_exec'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-core-2.99.2/lib/rspec/core/extensions/instance_eval_with_args.rb:16:in `instance_eval_with_args'
		     # ./bin/pact-provider-verifier/lib/vendor/ruby/2.1.0/gems/rspec-core-2.99.2/lib/rspec/core/example.rb:116:in `block in run'

One suggestion would be to automatically detect this cruft (anything starting with # ./bin) and discard the output, possibly configured as a flag or via DEBUG logging.

This should greatly increase readability and user experience.