Update required grunt version

Author: tomasz-oponowicz

README.md

@@ -5,7 +5,7 @@
 > Obfuscates JavaScript files using amazing [javascript-obfuscator](https://github.com/javascript-obfuscator/javascript-obfuscator).
 
 ## Getting Started
-This plugin requires Grunt `~0.4.5`
+This plugin requires Grunt `>=0.4.5`
 
 If you haven't used [Grunt](http://gruntjs.com/) before, be sure to check out the [Getting Started](http://gruntjs.com/getting-started) guide, as it explains how to create a [Gruntfile](http://gruntjs.com/sample-gruntfile) as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin and _javascript-obfuscator_ with this command: