docs: return 'pure' status

Author: KuznetsovRoman

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.org/gemini-testing/looks-same.svg?branch=master)](https://travis-ci.org/gemini-testing/looks-same)
 
-Node.js library for comparing images, taking into account human color
+Pure node.js library for comparing images, taking into account human color
 perception. It is created specially for the needs of visual regression testing
 for [`testplane`](http://github.com/gemini-testing/testplane) utility, but can be used
 for other purposes.