Made service provider compatible with Lumen

[robinvdvleuten]

Hi there,

I made a small change to make the library compatible with Lumen as seen here

Cheers!

[freekmurze]

Thank you.

Have you tested this in a Lumen application?

[robinvdvleuten]

@freekmurze I've tested it in a Lumen application with both the default serializer and a custom serializer. I'll fix the StyleCI issues in a bit.

[freekmurze]

Thanks! Don't mind the styling issues, styleci will take of that.