Explicitly note that this can't be used in the browser

Author: RyanZim

README.md

@@ -1,7 +1,7 @@
 Node.js - jsonfile
 ================
 
-Easily read/write JSON files.
+Easily read/write JSON files in Node.js. _Note: this module cannot be used in the browser._
 
 [![npm Package](https://img.shields.io/npm/v/jsonfile.svg?style=flat-square)](https://www.npmjs.org/package/jsonfile)
 [![build status](https://secure.travis-ci.org/jprichardson/node-jsonfile.svg)](http://travis-ci.org/jprichardson/node-jsonfile)