added a new section for the npm install fallback

Author: roblarsen

README.md

@@ -6,7 +6,8 @@ Quick start for HTML5 Boilerplate. Get up in running with one command.
 
 ## Getting Started
 
-You can get started using one of three options- `npx`, `npm init`, or `yarn create`
+You can get started using one of three options- `npx`, `npm init`, or
+`yarn create`
 
 Using `npx`
 
@@ -37,3 +38,23 @@ These commands are equivalent and do the following:
 1. Dowloads and installs the latest version of HTML5-Boilerplate
 2. Bundles site assets and tart a web server using [`parcel`](https://parceljs.org/)
 3. Opens a web browser pointed to http://localhost:1234/
+
+## Requirements
+
+`create-html5-boilerplate` is cross-platform. It works whereever node and npm work.
+The only requirements are for `npx`, which requires npm version 5.2 or greater and
+`npm init` which requires an npm version greater than 6.0. If you're stuck on an
+older version of npm you can still use `create-html5-boilerplate` by running the 
+following command to install the project globally.
+
+```sh
+npm install -g create-html5-boilperlate
+```
+
+Then you can use create-html5-boilerplate as in the following example
+
+```sh
+create-html5-boilperlate new-site
+cd new-site
+npm start
+```