Disable comment rule

https://github.com/thoughtbot/hound/issues/370
Return blank when file content request has problems

This addresses this issue: https://app.getsentry.com/app20126465herokucom/production/group/29003068
Introduce attr_extras

* Reduces boilerplate for simple Ruby objects
* Encourages good initializer practices (just initialize)
* Makes it easy to make immutable value objects

http://rubydoc.info/gems/attr_extras
Rename _filter to _action
Handle invalid YAML config