Improve install/usage instruction

It took me some time to figure out how I was supposed to get started, and there were some errors in the npm commands.
I hope this helps.

README.md

@@ -4,19 +4,17 @@
 
 This is part of the [node-firefox](https://github.com/mozilla/node-firefox) project.
 
-## Getting it
+## What you need
 
-### Clone it
+- [node.js](http://nodejs.org) and [git](http://git-scm.com/) installed on your machine
+- a Firefox OS simulator installed using [WebIDE](https://developer.mozilla.org/en-US/docs/Tools/WebIDE)
+- the files of this demo (clone this repo or download [the zip](https://github.com/mozilla/node-firefox-examples-gulp/archive/master.zip))
 
-`git clone https://github.com/mozilla/node-firefox-examples-gulp.git`
+## Build and run the example
 
-### Or download
-
-[the zip](https://github.com/mozilla/node-firefox-examples-gulp/archive/master.zip)
-
-## Initialising
-
-Install node.js if not installed yet, then cd to the directory and run `npm init`.
-
-To build the files into the `build` folder just do `npm start`. This will build the app into `build/index.html` which you can open with your browser to see it in action, unless you're using app APIs in which case you will need to run it in a Firefox OS simulator. There are two other gulp tasks available, `npm default-one` will launch the first simulator it can find and push the app to it, launch it, and watch for CSS changes. `npm default-all` will do the same but for all the simulators you have installed in your system.
+Install the dependencies by running `npm install` in the directory of this project.
 
+There are three npm scripts available:
+- `npm start` will build the app into `build/index.html` which you can open with your browser to see it in action, unless you're using app APIs in which case you will need to run it in a Firefox OS simulator,
+- `npm run default-one` will launch the first simulator it can find and push the app to it, launch it, and watch for CSS changes,
+- `npm run default-all` will do the same but for all the simulators you have installed in your system.