Incorrect Subclassing in Handler Documentation

[derks]

Need to reference use of super() and make sure example are using it... currently, the example here is broken.

• http://builtoncement.com/2.10/dev/interfaces_and_handlers.html#registering-handlers-to-an-interface

Ref: http://stackoverflow.com/questions/41361353/object-has-no-attribute-meta-in-python-cement-app

[subhashb]

@derks Will an explanation on how super() is involved and updating the handler example suffice to address this issue? I can give it a go.

[derks]

@subhashb Yeah, just a quick reference to point out that super() is required for any class functions that are being sub-classed/overridden... and ensuring the examples are using it.