Update Twitter Bootstrap upto v3.1.1.

_assets/vendor/bootstrap/grunt/shrinkwrap.js

@@ -0,0 +1,28 @@
+/*!
+ * Bootstrap Grunt task for generating npm-shrinkwrap.canonical.json
+ * http://getbootstrap.com
+ * Copyright 2014 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ */
+/*
+This Grunt task updates the npm-shrinkwrap.canonical.json file that's used as the key for Bootstrap's npm packages cache.
+This task should be run and the updated file should be committed whenever Bootstrap's dependencies change.
+*/
+'use strict';
+var canonicallyJsonStringify = require('canonical-json');
+var NON_CANONICAL_FILE = 'npm-shrinkwrap.json';
+var DEST_FILE = 'test-infra/npm-shrinkwrap.canonical.json';
+
+
+function updateShrinkwrap(grunt) {
+  // Assumption: Non-canonical shrinkwrap already generated by prerequisite Grunt task
+  var shrinkwrapData = grunt.file.readJSON(NON_CANONICAL_FILE);
+  grunt.log.writeln('Deleting ' + NON_CANONICAL_FILE.cyan + '...');
+  grunt.file.delete(NON_CANONICAL_FILE);
+  // Output as Canonical JSON in correct location
+  grunt.file.write(DEST_FILE, canonicallyJsonStringify(shrinkwrapData));
+  grunt.log.writeln('File ' + DEST_FILE.cyan + ' updated.');
+}
+
+
+module.exports = updateShrinkwrap;