Fix dompurify build and upgrade to new version

Gruntfile.js

@@ -307,7 +307,7 @@ module.exports = function(grunt) {
             },
             readSandbox: {
                 src: [
-                    'node_modules/dompurify/purify.js',
+                    'node_modules/dompurify/src/purify.js',
                     'node_modules/iframe-resizer/js/iframeResizer.contentWindow.min.js',
                     'src/js/controller/app/read-sandbox.js'
                 ],

package.json

@@ -25,7 +25,7 @@
     "browsersmtp": "https://github.com/whiteout-io/browsersmtp/tarball/master",
     "chai": "~1.9.2",
     "crypto-lib": "~0.2.1",
-    "dompurify": "~0.6.3",
+    "dompurify": "~0.7.3",
     "grunt": "~0.4.1",
     "grunt-angular-templates": "~0.5.7",
     "grunt-autoprefixer": "~0.7.2",