Override `p`

[seanlinsley]

Arbre uses para for <p> tags because p is a Ruby method, similar to puts. I understand the unwillingness to override Ruby methods, but I think it's less surprising than requiring people to read the Arbre documentation in order to create paragraph tags.

I propose that we release a final version for 1.x (1.99) that:

• warns that behavior will change for p
• deprecates para

As well, that we immediately release a 2.0 version with the method renamed from para to p.