I got some feedback from non-suppers that my utf-8 text attachments were
messed up. When I checked they (the MIME headers) lacked any info on charset,
which I believe should be set for text/*.

Here's a patch that uses the chardet gem to (try to) detect the appropriate charset
and sets it in the Content-Type header.

Can't guarantee its robustness - have only tried on a couple of text files and
one non-text file.

Please tell me if I should use some different way of sending patches... This git
flow is a bit new to me. (=
-- 
alge