Small changes to css to clean up code

web/react/components/file_upload.jsx

@@ -152,32 +152,26 @@ module.exports = React.createClass({
         if (this.props.postType === 'post') {
             $('.row.main').dragster({
                 enter: function() {
-                    $('.center-file-overlay').removeClass('invisible');
-                    $('.center-file-overlay').addClass('visible');
+                    $('.center-file-overlay').removeClass('hidden');
                 },
                 leave: function() {
-                    $('.center-file-overlay').removeClass('visible');
-                    $('.center-file-overlay').addClass('invisible');
+                    $('.center-file-overlay').addClass('hidden');
                 },
                 drop: function(dragsterEvent, e) {
-                    $('.center-file-overlay').removeClass('visible');
-                    $('.center-file-overlay').addClass('invisible');
+                    $('.center-file-overlay').addClass('hidden');
                     self.handleDrop(e);
                 }
             });
         } else if (this.props.postType === 'comment') {
             $('.post-right__container').dragster({
                 enter: function() {
-                    $('.right-file-overlay').removeClass('invisible');
-                    $('.right-file-overlay').addClass('visible');
+                    $('.right-file-overlay').removeClass('hidden');
                 },
                 leave: function() {
-                    $('.right-file-overlay').removeClass('visible');
-                    $('.right-file-overlay').addClass('invisible');
+                    $('.right-file-overlay').addClass('hidden');
                 },
                 drop: function(dragsterEvent, e) {
-                    $('.right-file-overlay').removeClass('visible');
-                    $('.right-file-overlay').addClass('invisible');
+                    $('.right-file-overlay').addClass('hidden');
                     self.handleDrop(e);
                 }
             });

web/react/components/file_upload_overlay.jsx

@@ -7,7 +7,7 @@ module.exports = React.createClass({
         overlayType: React.PropTypes.string
     },
     render: function() {
-        var overlayClass = 'file-overlay invisible';
+        var overlayClass = 'file-overlay hidden';
         if (this.props.overlayType === 'right') {
             overlayClass += ' right-file-overlay';
         } else if (this.props.overlayType === 'center') {