Remove useless mail event with entire that counts entire box as new after openBox

[freman]

var Imap = require('map');
var imap = new Imap(opts);

imap.once('ready', function() {
    imap.openBox('INBOX', true, function(err, box) {
        console.log('Got inbox', box.messages.total);
    });
});

imap.on('mail', function(new) {
    console.log('New mail', new);
});

Before this patch the above code would print out

Got inbox 5052
New mail 5052
# Then when an actual message came in
New mail 1

Now the code above prints

Got inbox 5052
# Then when an actual message comes in
New mail 1

[bengotow]

Any updates on this? It seems this is a pretty clean fix to #445, would be really great to merge it in.

[jstejada]

@mscdex any chance we could merge this in?