Merge pull request jwasham#363 from hiiakku/patch-1

Adding Challenge sites

Author: jwasham

README.md

@@ -1413,6 +1413,7 @@ Challenge sites:
 - [Geeks for Geeks](http://www.geeksforgeeks.org/)
 - [InterviewBit](https://www.interviewbit.com/invite/icjf)
 - [Sphere Online Judge (spoj)](http://www.spoj.com/)
+- [Codechef](https://www.codechef.com/)
 
 Challenge repos:
 - [Interactive Coding Interview Challenges in Python](https://github.com/donnemartin/interactive-coding-challenges)