docs(README.md): fix typo (Stadalone --> Standalone)

Author: gkalpak

README.md

@@ -176,7 +176,7 @@ This script will execute the end-to-end tests against the application being host
 development server.
 
 **Note:**
-Under the hood, Protractor uses the [Selenium Stadalone Server][selenium], which in turn requires 
+Under the hood, Protractor uses the [Selenium Standalone Server][selenium], which in turn requires 
 the [Java Development Kit (JDK)][jdk] to be installed on your local machine. Check this by running 
 `java -version` from the command line.