pytest doesn't provide --cov by default

Update the docs to explain how to use

Author: TurnrDev

README.md

@@ -34,6 +34,7 @@ coverage run tests.py
 ```
 #### pytest
 ```
+pip install pytest-cov
 pytest --cov=./
 ```
 #### nosetests
@@ -75,4 +76,4 @@ Cobertura reports can expire - Codecov will reject reports that are older than 1
 
 
 ## License
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+[![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fcodecov%2Fexample-python.svg?type=large)](https://app.fossa.com/projects/git%2Bgithub.com%2Fcodecov%2Fexample-python?ref=badge_large)