[matplotlib-devel] Small doc patch

Hello,
while reading the doc, I've encountered some little errors I've fixed
in the attached patch; nothing extremely difficult, but still worth
fixing :)

I'm even wondering if the svnmerge section in "Coding guide" is still
valid, since I've seen some emails passing here about that, but that's
too hard for me (as of now) :) .

Cheers,
-- 
Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi