Update grunt-html to v6.0.0.

Also remove the workaround for the old validator version.

[skip sauce]

Gruntfile.js

@@ -327,8 +327,7 @@ module.exports = function (grunt) {
           'The “datetime-local” input type is not supported in all browsers. Please be sure to test, and consider using a polyfill.',
           'The “month” input type is not supported in all browsers. Please be sure to test, and consider using a polyfill.',
           'The “time” input type is not supported in all browsers. Please be sure to test, and consider using a polyfill.',
-          'The “week” input type is not supported in all browsers. Please be sure to test, and consider using a polyfill.',
-          'Attribute “integrity” not allowed on element “script” at this point.' // Until https://github.com/jzaefferer/grunt-html/issues/86 gets fixed
+          'The “week” input type is not supported in all browsers. Please be sure to test, and consider using a polyfill.'
         ]
       },
       src: ['_gh_pages/**/*.html', 'js/tests/visual/*.html']

grunt/npm-shrinkwrap.json

@@ -1173,20 +1173,12 @@
       "resolved": "https://registry.npmjs.org/grunt-exec/-/grunt-exec-0.4.6.tgz"
     },
     "grunt-html": {
-      "version": "5.0.1",
-      "resolved": "https://registry.npmjs.org/grunt-html/-/grunt-html-5.0.1.tgz",
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/grunt-html/-/grunt-html-6.0.0.tgz",
       "dependencies": {
         "async": {
-          "version": "1.4.0",
-          "resolved": "https://registry.npmjs.org/async/-/async-1.4.0.tgz"
-        },
-        "chalk": {
-          "version": "1.1.0",
-          "resolved": "https://registry.npmjs.org/chalk/-/chalk-1.1.0.tgz"
-        },
-        "supports-color": {
-          "version": "2.0.0",
-          "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-2.0.0.tgz"
+          "version": "1.5.1",
+          "resolved": "https://registry.npmjs.org/async/-/async-1.5.1.tgz"
         }
       }
     },

package.json

@@ -48,7 +48,7 @@
     "grunt-contrib-watch": "~0.6.1",
     "grunt-eslint": "^17.1.0",
     "grunt-exec": "~0.4.6",
-    "grunt-html": "~5.0.0",
+    "grunt-html": "~6.0.0",
     "grunt-jekyll": "~0.4.2",
     "grunt-jscs": "~2.7.0",
     "grunt-line-remover": "0.0.2",