docs(rootScope): correct code examples
docs(exceptionHandler): document testing

Update src/ng/exceptionHandler.js

Here's an iniitla attempt at documenting how one might write a
test using $exceptionHandlerProvider. The key take-away is the use
of this pattern:

it(...

 module(...
   $exceptionHandlerProvider.mode('log');
 });

 inject(...
 );

});