Reduce size of banner images by about 75%

- Use 4 spaces indentation as per .editorconfig.
- Ignore some files gulp generates.

Author: sveitser

.gitignore

@@ -6,3 +6,7 @@ hackergarten.github.io.iml
 
 # external dependencies
 node_modules
+
+# generated by gulp
+feed.xml
+projects.html

pictures/header.1.jpg

@@ -3,12 +3,12 @@
 angular.module('hackergartenPage', ['ngDialog']);
 
 angular.module('hackergartenPage')
-	.directive('randomHeaderImage', function () {
-      return function (scope, element, attrs) {        
-        var image = "pictures/header." + Math.floor((Math.random()*4)+1) + ".png"
+    .directive('randomHeaderImage', function () {
+        return function (_scope, element, _attrs) {
+            var image = `pictures/header.${Math.floor((Math.random() * 4) + 1)}.jpg`;
 
-        element.css({
-            'background': 'url("' + image + '") center center no-repeat'
-        });
-      };
+            element.css({
+                'background': `url("${image}") center center no-repeat`
+            });
+        };
     });