Convert incoming text/* email payloads to unicode in be-handle-mail.

Convert incoming text/* email payloads to unicode in be-handle-mail.

Switched from cStringIO to StringIO in be-handle-mail because:
  (from http://docs.python.org/library/stringio.html)

  "Unlike the memory files implemented by the StringIO module, those
  provided by this [cStringIO] module are not able to accept Unicode
  strings that cannot be encoded as plain ASCII strings."

I'm not sure what all the fuss with sys.__stdin__ had been about in
Command.run(), but I took it out and everything still seems to work
;).

Also fix Makefail (again!) to install under $HOME by default.