IEx docs formatting

@pragdave Thank you! We are almost done there.

I have added one failing test case, could you please take a look?
In case you are interested, I found this error out by trying `h Kernel.SpecialForms`.

Also, what do you think if we limit the maximum width of the paragraph?
Which width you think would be ideal? 80 chars? 100 chars?
I can do the limiting once we agree on the maximum value.