Use yeoman.app for ionic font in Gruntfile template.

Author: huerlisi

templates/common/_Gruntfile.js

@@ -278,7 +278,7 @@ module.exports = function (grunt) {
       },
       fonts: {
         expand: true,
-        cwd: 'app/bower_components/ionic/release/fonts/',
+        cwd: '<%%= yeoman.app %>/bower_components/ionic/release/fonts/',
         dest: '<%%= yeoman.app %>/fonts/',
         src: '*'
       },