fix: Installation will now fail if your npm is not up to date

README.md

@@ -19,7 +19,8 @@ cross-platform way. Initially, it will provide a streamlined experience for deve
 
 ## Installation from npm
 
-First, make sure your `npm` is up to date:
+First, make sure your `npm` is up to date.
+You will need npm greater than version `3.0.0`:
 
     npm install --global npm
 
@@ -31,7 +32,7 @@ Install `web-ext`:
 
 You'll need:
 * [Node.js](https://nodejs.org/en/), 0.12 or higher
-* [npm](https://www.npmjs.com/), 3.x or higher
+* [npm](https://www.npmjs.com/), 3.0.0 or higher
 
 Optionally, you may like:
 * [nvm](https://github.com/creationix/nvm), which helps manage node versions

package.json

@@ -3,6 +3,11 @@
   "version": "1.1.0",
   "description": "A command line tool to help build, run, and test web extensions",
   "main": "dist/web-ext.js",
+  "engines": {
+    "node": ">=0.12",
+    "npm": ">=3.0.0"
+  },
+  "engine-strict": true,
   "bin": {
     "web-ext": "bin/web-ext"
   },