Moved dependencies to setup.py extras (#462)

.github/workflows/pythonapp.yml

@@ -19,7 +19,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -r requirements.txt
+        pip install .[test]
     - name: Lint with flake8
       run: |
         pip install -Iv enum34==1.1.6 # https://bitbucket.org/stoneleaf/enum34/issues/27/enum34-118-broken