Implement and_wrap_original

This probably needs more specs and needs features but this converts `and_call_original` into `and_wrap_original` then uses `and_wrap_original` to implement the old `and_call_original` (thus nicely proving it works!).

Closes #650.
This is accurate but I think the use case is more clear with something like:

``` ruby
# Decorates the stubbed method with the supplied block. The original method
# is passed to the block as the first argument (before any method call args) so
# that you can delegate to it while being able to change what args are passed to
# it and/or mutate the return value.
```