refactor: Put paste model in separate file

assets/templates/html/index.html.tmpl

@@ -8,6 +8,9 @@ the command line.
 
 ## USAGE
 
+    # Upload a file
+    curl -F'file=@yourfile.png' <a href="{{Request.Host}}">{{Request.Host}}</a>
+
     # Shorten a URL
     curl -F'shorten=http://example.com/some/long/url' <a href="{{Request.Host}}">{{Request.Host}}</a>