#4661: add bytes parsing and generation to email (email version bump to 5.1.0)

The work on this is not 100% complete, but everything is present to
allow real-world testing of the code.  The only remaining major todo
item is to (hopefully!) enhance the handling of non-ASCII bytes in headers
converted to unicode by RFC2047 encoding them rather than replacing them with
'?'s.
diff --git a/Misc/NEWS b/Misc/NEWS
index 7694e76..24b64f3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -92,6 +92,9 @@
 Library
 -------
 
+- Issue #4661: email can now parse bytes input and generate either converted
+  7bit output or bytes output.  Email version bumped to 5.1.0.
+
 - Issue #1589: Add ssl.match_hostname(), to help implement server identity
   verification for higher-level protocols.