Add a protocol buffer stream to the FileWriter

- also reuse the protocol buffer instead of generating a new instance each time
Clean up the Message string setter functions since strings are immutable
Make the buffer large enough to hold the max message and header structure
Add TcpWriter and updated FileWriter support for protocol buffer streams
Remove the debug dump and include the TcpOutput plugin config
comment typo
Define `PluginHelper` interface and use that instead of *PipelineConfig as
argument type for Input.Start().
Merge pull request #27 from mozilla-services/features/handoff-pipeline

Features/handoff pipeline
Merge branch 'dev' of github.com:mozilla-services/heka into dev
Add the FilterSpecification for more advanced message routing

- Initial checkin, it is functional but incomplete
-- No support for Fields
-- The current state machine performs a full evaluation i.e. no
short circuit
Add the InputRunnerSpec tests back in
Add short circuit evaluation to FilterSpecification
Add support for Fields in the FilterSpecification
First stat filter commit, along with updates to text parser for type refactoring.
Add stat filter so it can be used.
Set a better default for matched.
Set some other default fields to be usable during interpolation.
Merge pull request #29 from mozilla-services/features/stat-filter

Features/stat filter
Merge pull request #30 from mozilla-services/features/filterspec

Features/filterspec
Add spaces so license isn't part of package docs.