Pin pydocstyle version to less than 4.0.0 (#44)

pydocstyle 4.0.0 breaks flake8-docstrings 1.3.0
See: https://gitlab.com/pycqa/flake8-docstrings/issues/36

Author: gitanshu

setup.py

@@ -24,6 +24,9 @@
     'flake8-import-order',
     'pep8-naming',
     'pre-commit',
+    # pydocstyle 4.x breaks flake8-docstrings 1.3.0
+    # See https://gitlab.com/pycqa/flake8-docstrings/issues/36
+    'pydocstyle<4.0.0',
     'pylint',
     'pytest>=3.6',  # Required for pytest-cov on Python 3.6
     'pytest-cov',