Decode npm-notice heder according to the rfc2047 rule.

[sla100]

Currently server can send only 7-bit ASCII data in npm-notice header.

This code change will allow to send any Unicode message. The rfc2047 encoding it is used in similar place (Subject header) in electronic mail. Plain messages that do not contain a very specific phrase =?[...]?= will not be modified.

References

Fixes #37

[wraithgar]

I don't think this is something we need to do because the npm registry is not sending extended ascii characters in its npm-notice headers. They can't start doing it either because even if the npm cli were patched today, millions of folks are running versions of npm that can't display it. As it stands now npm registry implementations are going to have to continue only returning basic ascii as they do today.