make casperjs use local phantomjs

build/grunt-tasks/casper.js

@@ -7,6 +7,9 @@ module.exports = function (grunt) {
     var path = require('path')
     var done = this.async()
     var file = id ? id + '.js' : ''
+    // let casperjs use local phantomjs
+    process.env.PHANTOMJS_EXECUTABLE =
+      '../../node_modules/karma-phantomjs-launcher/node_modules/.bin/phantomjs'
     grunt.util.spawn({
       cmd: '../../node_modules/.bin/casperjs',
       args: ['test', '--concise', './' + file],