Implemented the attach addon

addons/fullscreen/fullscreen.css

@@ -0,0 +1,10 @@
+.xterm.fullscreen {
+    position: fixed;
+    top: 0;
+    bottom: 0;
+    left: 0;
+    right: 0;
+    width: auto;
+    height: auto;
+    z-index: 255;
+}

addons/fullscreen/fullscreen.js

@@ -0,0 +1,25 @@
+/*
+ * Fullscreen addon for xterm.js
+ *
+ * Implements the toggleFullscreen function.
+ *
+ * If the `fullscreen` argument has been supplied, then
+ * if it is true, the fullscreen mode gets turned on,
+ * if it is false or null, the fullscreen mode gets turned off.
+ *
+ * If the `fullscreen` argument has not been supplied, the
+ * fullscreen mode is being toggled.
+ */
+Terminal.prototype.toggleFullscreen = function (fullscreen) {
+  var fn;
+  
+  if (typeof fullscreen == 'undefined') {
+    fn = (this.element.classList.contains('fullscreen')) ? 'remove' : 'add';
+  } else if (!fullscreen) {
+    fn = 'remove';
+  } else {
+    fn = 'add';
+  }
+  
+  this.element.classList[fn]('fullscreen');
+}