Revert "Change the default font to Helvetica Neue"

This reverts commit b309ef25fd.

css/main.css

 }
 
 html, body, input, textarea, keygen, select, button {
-    font-family:    'Helvetica Neue',
+    font-family:    'open_sanslight',
+                    'Helvetica Neue',
                     Helvetica,
                     sans-serif !important;
 }

css/unsupported_browser.css

     height:100%;
     background-color: white;
     color: #424242;
-    font-family:    'Helvetica Neue',
-                    Helvetica,
-                    sans-serif;
+    font-family: 'open_sanslight', 'Helvetica Neue', Helvetica, sans-serif;
     font-size: 28px;
     margin:0;
     padding:0;