Update flood (and cleanup related to the additional testing)

- Modify the client SendMessage interface to include encoding and signing
- Add Encoding() to the client Encoder interface
- Combine signed/unsigned stream header encoding functions
- Add encoding support to UDP
- Update flood to include data corruption, variable length messages, and a mix of signed messages
- Update the JSON decoder to work with the Message JSON schema instead of the Metlog JSON Schema
- Fix findMessage bug to prevent it from returning msgOk when no record separator exists
- Set the Logger variable to the plugin name during sandbox message injection
Merge branch 'dev' into issue_63

Conflicts:
	pipeline/inputs.go
	pipeline/inputs_test.go
Fix issues with dev merge

- Add the decoder set back on the channel
- Undo the TcpInput ok check consolidation so he header is properly cleared
Incorporate review feeback

- reduce sender related code duplication by refactoring the client code
- remove the decoder name from the error message
- create flood docs
Merge pull request #102 from mozilla-services/issue_63

Update flood (and cleanup related to the additional testing)