Add support for `beforeNotify` callback
Add `setBeforeNotify` to README
Add Error APIs to README
Fix setIgnoreClasses anchor
Handle BeforeNotify exceptions
Fix the `beforeNotify` invocation

Check that the exception name hasn’t been set to ignored before
invoking the `beforeNotify` method.

Added some extra little convenience methods in Error.
Update README
Fix test
Document APIs in README
Support for multiple `beforeNotify` callbacks
Update README for multi `beforeNotify` callbacks
Fix old reference in README
Remove shouldIgnore from README

This method is technically rendered useless.
Merge pull request #16 from jacobmarshall/before-notify

Add support for `beforeNotify` callback