Added a blurb about error handling to the contrib guidelines.
Added a blurb about error handling to the contrib guidelines.

Fixes #317.

rafkhan/the-clusternator,rangle/the-clusternator,bennett000/the-clusternator,rangle/the-clusternator,alanthai/the-clusternator,rafkhan/the-clusternator,bennett000/the-clusternator,rangle/the-clusternator,alanthai/the-clusternator,bennett000/the-clusternator