add loading animation

Create _loader.scss

Update main.scss

Update _base.scss

Update gui.js

Update index.html

removed trailing spaces

removed trailing white spaces for real

lib/gui.js

@@ -48,6 +48,9 @@ function (chroma, Map, Sidebar, Tabs, Container, Meshstats, Legend, Linklist,
       }
     }
 
+    var loader = document.getElementsByClassName("loader")[0]
+    loader.classList.add("hide")
+
     contentDiv = document.createElement("div")
     contentDiv.classList.add("content")
     document.body.appendChild(contentDiv)