Update http -> https links in perf rnn demo (#175)

* update perf demo

* remove extra css file

* update make website

* update support message

* fix http https issue on perf rnn

Author: dsmilkov

demos/performance_rnn/performance_rnn.ts

@@ -94,9 +94,9 @@ const keyboardInterface = new KeyboardElement(container);
 
 const piano = new Piano({velocities: 4}).toMaster();
 
-const SALAMANDER_URL = 'http://storage.googleapis.com/learnjs-data/' +
+const SALAMANDER_URL = 'https://storage.googleapis.com/learnjs-data/' +
     'Piano/Salamander/';
-const CHECKPOINT_URL = 'http://storage.googleapis.com/learnjs-data/' +
+const CHECKPOINT_URL = 'https://storage.googleapis.com/learnjs-data/' +
     'checkpoint_zoo/performance_rnn';
 
 const isDeviceSupported = demo_util.isWebGLSupported() && !demo_util.isSafari();