Collapses 2.13 and 2.14 into one and changes the wording of the rule to ...

...be positive.

Also includes minor reformatting.

Also reformulates 1.9 in the same wording as 2.13

As discussed in #106, with positive rule focus suggested by @DougLea

Review by @reactive-streams/contributors 
What about:

 | <a name="1.6">6</a> | If a `Publisher` signals either `onError` or `onComplete` on a `Subscriber`, that `Subscriber`’s `Subscription` MUST be considered canceled and it is REQUIRED that no further signals to it occur.