Added decoding of messages

Also moved things out to their own files and setup require()s to bring it all together.

messages/SLLoginMessage.js

@@ -0,0 +1,12 @@
+const SLMessage = require('./SLMessage.js').SLMessage;
+
+exports.SLLoginMessage = class SLLoginMessage extends SLMessage {
+  constructor() {
+    super(0, 27);
+    this.writeInt32LE(348); // schema
+    this.writeInt32LE(0); // connection type
+    this.writeSLString('node-screenlogic'); // version
+    this.writeSLBuffer(Buffer.alloc(16)); // encoded password. empty/unused for local connections
+    this.writeInt32LE(2); // procID
+  }
+}