Release v0.6.0

Changelog:

- Implement a pythonic way of signing a message using
  patatt.rfc2822_sign(bytes)
- Work around inconsistencies in git-mailinfo when there are in-body
  headers and the message uses CRLF endings
-----BEGIN PGP SIGNATURE-----

iHUEABYKAB0WIQR2vl2yUnHhSB5njDW2xBzjVmSZbAUCYwO1ZAAKCRC2xBzjVmSZ
bLqUAP9MZ1S/r4JzNj2efBYtxAaFsmvHG9C5wXhVEcF7VTdyKQEAjKc/bRnaaRqQ
WUMTw64W92rkpM0xdkB65kVVgLIzmQw=
=zaP0
-----END PGP SIGNATURE-----