Update README for h2 flags

Author: tony19

README.md

@@ -28,6 +28,10 @@ Navigate to `localhost:8080/components/my-element/demo.html`
   * `-o` Opens your default browser to an initial page, e.g. "demo" or "index.html"
   * `-b <browsername>` use this browser instead of default (ex: 'Google Chrome Canary')
   * `-H <hostname>` use this hostname instead of localhost
+  * `-h <protocol>` The server protocol to use {`h2`, `https/1.1`, `http/1.1`}. `h2` requires Node 5+.
+  * `-k <path>` Path to TLS certificate private key file for https. Defaults to "key.pem".
+  * `-t <path>` Path to TLS certificate file for https. Defaults to "cert.pem".
+  * `-m <path>` Path to h2-push manifest
 
 ## Run Tests