overwriteChainableMethod documentation out of date

[jasonkarns]

The method signature is shown with 3 args, but lists 4 params. And the examples don't really describe the difference between args 3 and 4.

[keithamus]

Thanks for the issue @jasonkarns, you're totally right too - the documentation could be loads better. If you fancy writing a PR for it I'd love to see one!

The documentation can be located here (L7-37), just above the function definition.