Remove grunt-shell dependency and use npm script (#327)

* Remove grunt-shell dependency and use npm script

* Use --silent here to reduce NPM error message output

This then outputs `npm ERR! Test failed.  See above for more details.`.

Gruntfile.js

@@ -49,25 +49,16 @@ module.exports = function(grunt) {
           loadPath: [
             './stylesheets'
           ],
-          style: 'nested',
+          style: 'nested'
         }
-      },
-    },
-    shell: {
-      multiple: {
-        command: [
-          'bundle',
-          'bundle exec govuk-lint-sass stylesheets'
-        ].join('&&')
       }
     }
   });
 
   grunt.loadNpmTasks('grunt-contrib-clean');
   grunt.loadNpmTasks('grunt-contrib-jasmine');
   grunt.loadNpmTasks('grunt-contrib-sass');
-  grunt.loadNpmTasks('grunt-shell');
 
-  grunt.registerTask('test', ['sass', 'clean', 'jasmine', 'shell']);
+  grunt.registerTask('test', ['sass', 'clean', 'jasmine']);
   grunt.registerTask('default', ['test']);
 };

package.json

@@ -8,10 +8,10 @@
     "grunt-contrib-clean":"~0.6.0",
     "grunt-contrib-jasmine": "^1.0.0",
     "grunt-contrib-sass": "0.7.4",
-    "grunt-shell": "^1.1.2",
     "jquery": "~1.11.3"
   },
   "scripts": {
-    "test": "node_modules/.bin/grunt test"
+    "test": "grunt test && npm run lint --silent",
+    "lint": "bundle && bundle exec govuk-lint-sass stylesheets"
   }
 }