Adds -g for node-gyp install in website.

index.html

@@ -100,7 +100,7 @@ <h1>Getting Started Guide</h1>
         <div class="page-body">
           <p>Make sure you have the latest Node.js installed.</p>
           <p>Before you continue, install node-gyp using npm (node's package manager).</p>
-          <pre>$ npm install node-gyp</pre>
+          <pre>$ npm install node-gyp -g</pre>
           <p>Again use npm to install AppJS.</p>
           <pre>$ npm install appjs</pre>
           <p>AppJS tries to install dependencies based on the platform you are working with.</p>