Add support for statmetric message to emit stats data in message fields as well as
or instead of in the message payload.
Merge branch 'dev' into features/issue_223
Merge branch 'dev' into features/issue_223
Add initial StatsdInput test code, along w/ trivial changes to StatsdInput itself to
support same.
Merge branch 'dev' into features/issue_223 and comment out more tests.

Conflicts:
	pipeline/all_specs_test.go
Merge pull request #245 from mozilla-services/features/issue_223

Features/issue 223

r+ @bbangert