+ in email addresses - edge case with a lot of variation between implementations.

[Tomas Doran]

http://babelmark.bobtfish.net/?markdown=%3Ca%2Bb%40c.org%3E&normalize=on

Only Python markdown, Pandoc, discount and PEG markdown seem to get  
this 'right'.

As a + is perfectly valid in email addresses, I'm going to fix this  
in my modules.

This was reported to me via the cpan.org RT (37909), and I thought  
I'd share as it's a good one in Babelmark.

Cheers
Tom