Added append LITERAL+ extension support
Added append LITERAL+ extension support

The client will automatically detect if the server supports
LITERAL+ during an append, and if so, will immediately send
the message data. This allows messages to be append to a
Microsoft Exchange server.

Yubin/node-imap,phgrey/node-imap,mscdex/node-imap,rltvty/node-imap,ClientSuccess/node-imap,modulexcite/node-imap,craigp/node-imap,signpost/node-imap,parro-it/node-imap,potato620/node-imap,icemilo/node-imap