Merge pull request #496 from Montana/patch-1

Fix broken test command in contributing section.

Author: brianr

README.md

@@ -81,4 +81,7 @@ For bug reports, please [open an issue on GitHub](https://github.com/rollbar/pyr
 4. Push to the branch (```git push origin my-new-feature```)
 5. Create new Pull Request
 
-Tests are in `rollbar/test`. To run the tests: `python setup.py test`
+Tests are in `rollbar/test`. To run them:
+
+    pip install -e . --group test
+    pytest