change the get_gateway and get_integration

[nooperpudd]

change the gateway and integration find the gateway and integration
find the modules.

[tuxcanfly]

I can allow this for more flexibility in naming the gateway/integration classes, although I'm not convinced it is really necessary. When you're writing a custom gateway, you control the class name so you might as well name it as documented i.e like MyCustomGateway. Is there some case where you cannot name a class as like that?

Also, highly unlikely but if someone has another Gateway at the end of a module, this upgrade will pick up the last gateway class, so it risks backward compatibility.

[nooperpudd]

@tuxcanfly Fine.

[tuxcanfly]

@nooperpudd Thanks for reporting the issue, I'm thinking this should be fixed by removing the magic and simplifying the backend loading logic. See #111