create command for getting parts of the zen of python

[skrungly]

it would be nice to be able to get specific parts of the zen of python from a command. for example,

!zen 13 would retrieve the fourteenth line (because we index from zero, obviously).

!zen namespaces would search for the string "namespaces", and produce the line which matches best.

!zen without any arguments would still produce the entire thing in the same way that the zen tag does.

i think this is reasonably simple, and could come in handy from time to time. :D

edit: also, i'd quite like to implement this. seems simple enough while i get used to all of the new changes since last year :D