Adding comment explainning why we are fixing pluggy to 0.7.1 version

Author: Francisco Javier Franco Algarrada

setup.py

@@ -83,6 +83,7 @@
         "bumpversion>=0.5.3,<1",
         "wheel",
         "setuptools>=36.2.0",
+        #Fixing this dependency due to: pytest 3.6.4 has requirement pluggy<0.8,>=0.5, but you'll have pluggy 0.8.0 which is incompatible.
         "pluggy==0.7.1",
         "tox==2.7.0",
         "twine",