Port #18402 to v3: s/grunt-sed/npm script/g

Fixes #18338
[skip sauce]
[skip validator]

package.json

@@ -14,6 +14,7 @@
   "homepage": "http://getbootstrap.com",
   "author": "Twitter, Inc.",
   "scripts": {
+    "change-version": "node grunt/change-version.js",
     "test": "grunt test"
   },
   "style": "dist/css/bootstrap.css",
@@ -52,10 +53,10 @@
     "grunt-jekyll": "~0.4.2",
     "grunt-jscs": "~2.3.0",
     "grunt-saucelabs": "~8.6.1",
-    "grunt-sed": "twbs/grunt-sed#v0.2.0",
     "load-grunt-tasks": "~3.3.0",
     "markdown-it": "^5.0.0",
     "npm-shrinkwrap": "^200.4.0",
+    "shelljs": "^0.5.3",
     "time-grunt": "^1.2.1"
   },
   "engines": {