CONTRIBUTING.md (#43)(fixes #34)

Author: f3ath

CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contributing to the project
+Thank you for you interest! Here are some key guidelines.
+
+## PSR
+We want to follow the latest actual [PSR](http://www.php-fig.org/psr/) standards.
+
+## Tests are documentation
+The use cases and library's API must be expressed in a form of tests. We use PHPUnit, but it does not mean all tests
+are expected to be unit tests. No logic must be written without a supporting test.