Added a decodeSection function to mime.go that uses go-qprintable to
parse quoted-printable emails or MIME parts, fixes#7
Added a very basic TextToHtml converter to provide nicer rending of text
message bodies.
Messages with a MIME text/html MIME part will now be displayed with an
`HTML` button above them that will open another window and render the
HTML when clicked.
There is no sanitization performed, and inline attachment display is
not support.
This closes#2
