update node/npm requirements [ci skip]

Require minimum npm 2.14.2, shipped with node 4.0.0

If node v4 is required, it's silly to require npm@1. (+1 squashed commit)
Squashed commits:
[796190e] Update to require "Node.js v4 or newer".

Just update the documentation to remove support for node `<4`.

The current version of `mocha` pulls in dependencies which use arrow functions which fail in earlier versions of node.

See https://travis-ci.org/sirreal/mocha/builds/299600162, where I forked `mocha` and added tests for earlier versions.

docs/index.md

@@ -89,7 +89,7 @@ or as a development dependency for your project:
 $ npm install --save-dev mocha
 ```
 
-> To install Mocha v3.0.0 or newer with `npm`, you will need `npm` v1.4.0 or newer.  Additionally, to run Mocha, you will need Node.js v0.10 or newer.
+> To install Mocha v3.0.0 or newer with `npm`, you will need `npm` v2.14.2 or newer.  Additionally, to run Mocha, you will need Node.js v4 or newer.
 
 Mocha can also be installed via [Bower](http://bower.io) (`bower install mocha`), and is available at [cdnjs](https://cdnjs.com/libraries/mocha).