Add intro message/warning

simulator-sketch.js

@@ -1,3 +1,13 @@
+// This is a sketch of a simulator for my paper computer,
+// made for two purposes:
+// 
+// (1) figuring out the basic structure for a simple simulator
+// (2) testing some simple programs (hopefully)
+//
+// NOTA BENE: this simple version makes naive use of
+// Javascript numbers for opcodes, and a Javascript array
+// for the computer's "memory." This may cause some problems.
+
 function CPU(mem) {
   this.memory = mem;
   this.running = false;