added rackless exception handler and issue renderer
added rackless classes to the gem via require
missing namespace on RacklessExceptionHandler
rackless now uses symbols for key in the env hash
removed unnecessary app root method from rackless. added tests.
Merge pull request #18 from amaabca/rackless_exception_handling

Rackless exception handling
Better matcher for headers
Renamed to blacklisted

ignored exceptions and filtered http_headers renamed
Updated README