New API Debug Mode. 

If enabled, any exceptions handled by Dingo Router will add an additional debug key filled with exception information.

This PR aims to solve the issue brought up by #69. There are somethings I am not sure about, such as the Config facade use, or the adding of HTTP Request information.

Up to discussing further to refine this. We could make this super basic, or even go as far as to write in custom formatting for the trace output. But don't want to overkill this.
That's what I was thinking of doing. Just seemed like overkill for a single if statement, but might be necessary to get the tests to pass. One those, works if I test it practically, but didn't think it would fail the PHPUnit tests situations.