Regenerate package-lock.json with NPM 5.5.1 (#774)

Also include a note in the README to use NPM 5.5.1 to avoid deployment issues in
the future.

README.md

@@ -8,10 +8,20 @@ Prerequisites
 -------------
 * Python 2.7.x (not tested with Python 3.x)
 * [gettext](http://www.gnu.org/software/gettext/)
-* [node](https://nodejs.org) 5.2.x
-* [npm](https://www.npmjs.org/)
+* [node](https://nodejs.org) 8.9.3
+* [npm](https://www.npmjs.org/) 5.5.1
 * [JDK 7+](http://openjdk.java.net/)
 
+Warning: You must have NPM version 5.5.1. Using another version might result in
+a different `package-lock.json` file. Committing those changes might break our
+deployments which use NPM 5.5.1 and expect no changes after running `npm
+install`. [nodeenv](https://github.com/ekalinin/nodeenv) or
+[n](https://github.com/tj/n) are tools that you can use to work on different
+Node.js and NPM versions than your system installed versions.
+
+We have a TODO to set-up the development environment with a Docker container so
+that you will not have to manage Node and NPM versions yourself.
+
 Getting Started
 ---------------
 1. Get the code (e.g. clone the repository).

package.json

@@ -30,7 +30,7 @@
     "datatables": "1.10.13",
     "datatables-bootstrap3-plugin": "0.5.0",
     "edx-pattern-library": "0.16.6",
-    "edx-ui-toolkit": "git://github.com/edx/edx-ui-toolkit#29759050aff2f4f3cb6921432855ad057bd69bb1",
+    "edx-ui-toolkit": "git://github.com/edx/edx-ui-toolkit.git#29759050aff2f4f3cb6921432855ad057bd69bb1",
     "extract-text-webpack-plugin": "3.0.2",
     "file-loader": "0.11.2",
     "font-awesome": "4.6.3",
@@ -61,7 +61,7 @@
     "axe-core": "2.6.1",
     "babel-eslint": "7.2.3",
     "babel-plugin-istanbul": "4.1.6",
-    "edx-custom-a11y-rules": "edx/edx-custom-a11y-rules#ff77f203ef5d9534c6200cc141e9d150155d0e12",
+    "edx-custom-a11y-rules": "github:edx/edx-custom-a11y-rules#ff77f203ef5d9534c6200cc141e9d150155d0e12",
     "eslint": "3.19.0",
     "eslint-config-edx": "2.0.1",
     "eslint-config-edx-es5": "3.0.0",