UX: Clarify call to action on landing page.

Author: alexander-alvarez

app/templates/application.hbs

@@ -72,7 +72,7 @@
             <i class="fa fa-exclamation-triangle"></i>
           </h1>
           <h2 class="subtitle">
-            Please upload data.
+            Run <code>BROCCOLI_VIZ=1 ember build</code> and please upload data to begin your analysis.
           </h2>
         </a>
       </div>