Merge pull request #16 from tristanbes/master

Added KnpBundle badge
Updating subject to be more descriptive
Removing unused variable
Adding a space in the subject
Putting a limit on the subject length
Use status code (400/500) instead of error code in subject
Merge pull request #17 from ollietb/error_subject

Updating subject to be more descriptive
Remove request dependency

For mail sent outside of the request scope
Add support for 2.3
Add example to use a custom mailer
Update README.md

Add possibility to define an extra mailer (example : to send error mails by php mail function instead of smtp)
Fixed CS
Added a new feature to disable email sending for errors raised by a given class.
Merge branch 'tristanbes-master' of https://github.com/tristanbes/ErrorNotifierBundle into tristanbes-tristanbes-master