Use Buffer concatenation for binary data instead of binary strings. Fixes Node.js v6.0.0 breakage. (#1001)

lib/client.js

@@ -84,7 +84,7 @@ Client.prototype.connect = function(callback) {
   //password request handling
   con.on('authenticationMD5Password', checkPgPass(function(msg) {
     var inner = Client.md5(self.password + self.user);
-    var outer = Client.md5(inner + msg.salt.toString('binary'));
+    var outer = Client.md5(Buffer.concat([new Buffer(inner), msg.salt]));
     var md5password = "md5" + outer;
     con.password(md5password);
   }));