support uu encoding

fixes #755 

@jeremy @bf4 @mikel 
was part of our legacy email structure, no idea where it came from, but
works with the attachments we have seen so far, which are prefixed with
"begin 644 Invoice.pdf" etc

On Thu, Oct 23, 2014 at 7:09 PM, Benjamin Fleischer <
notifications@github.com> wrote:

> In lib/mail/encodings/unix_to_unix.rb:
>
> > @@ -0,0 +1,17 @@
> > +module Mail
> > +  module Encodings
> > +    module UnixToUnix
> > +      NAME = "x-uuencode"
> > +
> > +      def self.decode(str)
> > +        str.sub(/\Abegin \d+ [^\n]*\n/, '').unpack('u').first
>
> Just curious if there is a reference you looked at to generate this
> expression.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/mikel/mail/pull/796/files#r19320162>.
>