Upgrade xterm.js to 3.0.1

Closes jupyter/notebook#2850

bower.json

@@ -24,6 +24,6 @@
     "requirejs-plugins": "~1.0.3",
     "text-encoding": "~0.1",
     "underscore": "components/underscore#~1.8.3",
-    "xterm.js": "sourcelair/xterm.js#~2.9.2"
+    "xterm.js": "https://unpkg.com/xterm@~3.0.1/dist/xterm.js"
   }
 }