Add support for custom exceptions

[bakura10]

This PR brings support for custom exceptions, so that you can trigger custom exceptions in user land code, and map it to HTTP exception that can be interpreted by ZfrRest.

I'm wondering if we couldn't do another approach here, so that this listener is able to interpret ANY exceptions (even those not in the $exceptionMap). For those exception, it would create a generic ServerErrorException, with the message extracted from the exception. The reason is that we'd like to receive response from ZfrRest for any exception. If people forgot to add a specific exception they throw in ZfrRest, then this listener will do nothing. But I'm not sure.

ping @Ocramius

[coveralls]

Coverage decreased (-0.51%) when pulling 35642d1 on custom-exception into 175fa75 on master.

[danizord]

I think this can be solved more easily with inheritance:

namespace Application\Exception;

use ZfrRest\Http\Exception\Client\NotFoundException;

class CustomerNotFound extends NotFoundException
{
}

or

namespace Application\Exception;

use ZfrRest\Http\Exception\HttpExceptionInterface;

class SomethingIsWrong implements HttpExceptionInterface
{
    // My custom HTTP Error, e.g http://httpstatusdogs.com/420-enhance-your-calm
}

[bakura10]

This does not work with exceptions thrown by third-party modules or if you throw exceptions from a third-party module (for instance if you throw UnauthorizedException from ZfcRbac). Even with your own exceptions, you may not want tie all your exceptions to ZfrRest.

[coveralls]

Coverage decreased (-0.51%) when pulling e52eee5 on custom-exception into 175fa75 on master.

[danizord]

Hmm, having said that. The catch-all approach seems more reasonable to me.

[Ocramius]

Cast to (string)

[bakura10]

I'm not really satisfied with it. The problem is that I really want this listener to catch all the exception so:

1. If exception is already a ZfrRest exception => OK.
2. If the exception is in the exception map, then we can create a ZfrRest exception from it.
3. Otherwise, we set a 500 error code (server error).

[Ocramius]

@bakura10 the default exception handler already sets a 500 error code. I think it's simply not our job.

If we can avoid doing more work than needed, then it's ok

[bakura10]

Ok, I've updated. Looks merge able?

[Ocramius]

@bakura10 looks ok, but my feedback on the code is still missing comments/patching

[bakura10]

Ok, merging for now then.

[coveralls]

Coverage decreased (-0.51%) when pulling ab086e1 on custom-exception into 175fa75 on master.