docs: update Node.js version in readme

Author: braydonf

README.md

@@ -10,7 +10,7 @@ Infrastructure to build Bitcoin and blockchain-based applications for the next g
 
 ## Getting Started
 
-Before you begin you'll need to have Node.js v0.12 installed. There are several options for installation. One method is to use [nvm](https://github.com/creationix/nvm) to easily switch between different versions, or download directly from [Node.js](https://nodejs.org/).
+Before you begin you'll need to have Node.js v4 or v0.12 installed. There are several options for installation. One method is to use [nvm](https://github.com/creationix/nvm) to easily switch between different versions, or download directly from [Node.js](https://nodejs.org/).
 
 ```bash
 npm install -g bitcore