Font size and fullscreen (#120)

* Allow to change terminal font size in settings.
Allow to enter fullscreen mode with alt+enter.

* Fix size issues

www/assets/xterm-addons/fullscreen.js

@@ -0,0 +1,50 @@
+/**
+ * Fullscreen addon for xterm.js
+ * @module xterm/addons/fullscreen/fullscreen
+ * @license MIT
+ */
+(function (fullscreen) {
+  if (typeof exports === 'object' && typeof module === 'object') {
+    /*
+     * CommonJS environment
+     */
+    module.exports = fullscreen(require('../../xterm'));
+  } else if (typeof define == 'function') {
+    /*
+     * Require.js is available
+     */
+    define(['../../xterm'], fullscreen);
+  } else {
+    /*
+     * Plain browser environment
+     */
+    fullscreen(window.Terminal);
+  }
+})(function (Xterm) {
+  var exports = {};
+
+  /**
+   * Toggle the given terminal's fullscreen mode.
+   * @param {Xterm} term - The terminal to toggle full screen mode
+   * @param {boolean} fullscreen - Toggle fullscreen on (true) or off (false)
+   */
+  exports.toggleFullScreen = function (term, fullscreen) {
+    var fn;
+
+    if (typeof fullscreen == 'undefined') {
+      fn = (term.element.classList.contains('fullscreen')) ? 'remove' : 'add';
+    } else if (!fullscreen) {
+      fn = 'remove';
+    } else {
+      fn = 'add';
+    }
+
+    term.element.classList[fn]('fullscreen');
+  };
+
+  Xterm.prototype.toggleFullscreen = function (fullscreen) {
+    exports.toggleFullScreen(this, fullscreen);
+  };
+
+  return exports;
+});