"Plugin" or "hook" system

[boennemann]

There are two uses for custom hooks I can currently think of:
Custom verification for the release (e.g. #7) and manipulation of the changelog/codenames.

I could imagine something like this: One has to define the verifyrelease and/or the changelog scripts inside the package.json. semantic-release sends some information over stdin and uses stdout/exit codes to process the information generated.