Add lint configuration and run in CI (Qiskit#27)

This commit adds a lint configuration based on the current pattern used
in upstream Qiskit. Leverage black for auto code formatting and then
pylint for a deeper analysis and catch common issues. The code style is
updated to then conform to these guidelines.

Fixes Qiskit#23

.github/workflows/main.yml

@@ -33,6 +33,20 @@ jobs:
           python -m pip install -U tox setuptools virtualenv wheel
       - name: Install and Run Tests
         run: tox -e py
+  lint:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: setup-python-3.7
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+      - name: install-requirements
+        run: |
+          python -m pip install --upgrade pip tox virtualenv wheel
+      - name: docs
+        run: tox -e lint
   docs:
     name: docs
     runs-on: ubuntu-latest
@@ -45,8 +59,7 @@ jobs:
       - name: install-requirements
         run: |
           sudo apt-get install -y graphviz pandoc
-          python -m pip install --upgrade pip tox
-          python -m pip install -e .
+          python -m pip install --upgrade pip tox virtualenv wheel
       - name: docs
         run: tox -e docs
       - name: Compress Artifacts