Add mention of Mozilla incubation to about page

Author: benfrancis

about/index.html

@@ -59,7 +59,7 @@ <h1>The Web of Things</h1>
 
       <section id="webthings-section" class="dark-section">
         <h1>WebThings</h1>
-        <p>WebThings is an open source implementation of the Web of Things, including the WebThings Gateway, WebThings Framework and WebThings Cloud.</p>
+        <p>WebThings is an open source implementation of the Web of Things, including the WebThings Gateway, WebThings Framework and WebThings Cloud. The WebThings project was incubated at <a href="https://mozilla.org">Mozilla</a> for four years, before being spun out as an independent open source project.</p>
         <img src="images/webthings_block_diagram.png" class="illustration" alt="Illustration of things created with the WebThings Framework, connected to WebThings Cloud via WebThings Gateway. "/>
       </section>