Obfuscate plain email text (no link) and don't replace text

Obfuscate plain email text (no link)
Don't replace <a href="mailto:"> tag content anymore
Don't parse non-HTML (CSS, JS, ...) requests anymore
Use beautifulsoup to ease tag manipulation
Make obfuscation more robust
This refs collective/collective.geotransform#4 and collective/collective.geotransform#8