Added XOR gate

console.js

@@ -0,0 +1,20 @@
+runTests = (label, network, tests) => {
+  console.log(`--- ${label}`);
+  for (test of tests) {
+    console.log(`${label} test ${JSON.stringify(test)}: ${network.run(test)}`);
+  }
+}
+
+netXOR = new brain.NeuralNetwork();
+netXOR.train([
+  { input: [0, 0], output: [0] },
+  { input: [0, 1], output: [1] },
+  { input: [1, 0], output: [1] },
+  { input: [1, 1], output: [0] }
+]);
+runTests("XOR gate", netXOR, [
+  [0,0],
+  [0,1],
+  [1,0],
+  [1,1]
+]);