Update index.html

Added copy to home page to indicate site is under construction.

index.html

@@ -76,9 +76,9 @@
     <div class="row">
       <div class="col-sm-12">
         <p>
-          # Currently under construction. See docs
+          <b>Currently under construction.</b> See docs
           <a target="_blank" href="http://bokeh.org">here</a>.
-          This hosts examples of applications built using
+          This site hosts examples of applications built using
           <a target="_blank" href="http://bokeh.org">Bokeh</a>, a library for building data visualizations
           and applications in the browser from <a target="_blank" href="https://www.python.org">Python</a>
           (and other languages), without writing JavaScript.