Update Extension.__init__ doc examples to list *args, **kwargs.
Update Extension.__init__ doc examples to list *args, **kwargs.

Our extension docs weren't showing the requirements for *args, **kwargs,
which are needed as of 1.7 RC 1. List them in all the examples.

1tush/reviewboard,beol/reviewboard,1tush/reviewboard,sgallagher/reviewboard,1tush/reviewboard,davidt/reviewboard,davidt/reviewboard,reviewboard/reviewboard,bkochendorfer/reviewboard,1tush/reviewboard,custode/reviewboard,KnowNo/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,1tush/reviewboard,chipx86/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,1tush/reviewboard,beol/reviewboard,1tush/reviewboard,beol/reviewboard,sgallagher/reviewboard,brennie/reviewboard,1tush/reviewboard,custode/reviewboard,beol/reviewboard,brennie/reviewboard,custode/reviewboard,KnowNo/reviewboard,davidt/reviewboard,brennie/reviewboard,chipx86/reviewboard,brennie/reviewboard,chipx86/reviewboard,1tush/reviewboard,custode/reviewboard,sgallagher/reviewboard,bkochendorfer/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard,KnowNo/reviewboard,KnowNo/reviewboard,davidt/reviewboard