Add heka-cat

A command line utility for counting, viewing, filtering, and extracting
Heka protobuf logs.
gofmt main.go
Merge branch 'dev' into heka-cat

Conflicts:
	CHANGES.txt
Fix default output
Add corruption detection reporting
Include the unmarshalling error message and skip the match attempt
Update the usage documentation te clarify the offset is in bytes
Merge pull request #653 from mozilla-services/heka-cat

Heka cat