HTML Links can break in quoted printable email output

When sending a HTML email that uses quoted printable transfer encoding (ActionMailer default), links can break when the line is split before a period in the link due to leading periods being removed twice, the quoted printable encoding adds an extra period as specified in the RFC, giving 2 to start with, these are then both removed, 

once by event machine
https://github.com/eventmachine/eventmachine/blob/master/lib/em/protocols/smtpserver.rb#L547

and then a second time by mailcatcher.
https://github.com/sj26/mailcatcher/blob/master/lib/mail_catcher/smtp.rb#L39

A simple script to repllicate the issue can be found here,
https://gist.github.com/JWells/5519294