Add CheckiO, Codewars, HackerRank, Codility and Contributing instruct…

…ions

CONTRIBUTING.md

@@ -0,0 +1,8 @@
+# Contribution Guidelines
+
+Please ensure your [pull request](https://github.com/mauriciovieira/awesome-challenges/pulls) adheres to the following guidelines:
+
+- Make an individual pull request for each suggestion.
+- Chose corresponding section (Community or Company) for your suggestion.
+- Use the following format for commit message: `Add Website Name`.
+- List, after your addition, should be alphabetically.

README.md

@@ -0,0 +1,20 @@
+# Awesome Challenges
+
+A curated list of algorithmic challenges websites.
+
+- Communities
+  - [CheckiO](http://www.checkio.org/)
+  - [Codewars](http://www.codewars.com/)
+  - [HackerRank](https://www.hackerrank.com/)
+
+- Companies
+  - [Codility](https://codility.com/programmers/challenges/)
+
+
+## License
+
+Based on [bayadin/awesome-awesomeness](https://github.com/bayandin/awesome-awesomeness) repository.
+
+[![Creative Commons License](http://i.creativecommons.org/l/by/4.0/88x31.png)](http://creativecommons.org/licenses/by/4.0/)
+
+This work is licensed under a [Creative Commons Attribution 4.0 International License](http://creativecommons.org/licenses/by/4.0/).