feat(app): imagemin handles gifs

Update Gruntfile to let imagemin handle gifs

Author: eddiemonge

Diff for: templates/common/Gruntfile.js

@@ -195,7 +195,7 @@ module.exports = function (grunt) {
         files: [{
           expand: true,
           cwd: '<%%= yeoman.app %>/images',
-          src: '{,*/}*.{png,jpg,jpeg}',
+          src: '{,*/}*.{png,jpg,jpeg,gif}',
           dest: '<%%= yeoman.dist %>/images'
         }]
       }
@@ -263,7 +263,7 @@ module.exports = function (grunt) {
             '*.{ico,png,txt}',
             '.htaccess',
             'bower_components/**/*',
-            'images/{,*/}*.{gif,webp}',
+            'images/{,*/}*.{webp}',
             'fonts/*'
           ]
         }, {