modified travis.yml to enforce style Black/Flake8

.travis.yml

@@ -3,6 +3,26 @@ language: python
 python:
   - "3.6"
   - "3.7"
+
+matrix:
+  fast_finish: true
+    - name: "Code Style (Black/Flake8)"
+      install:
+        - pip install --upgrade pip
+        - pip install black
+        - pip install flake8
+      script:
+        # Black code style
+        - black --check --diff pytorch_widedeep tests examples setup.py
+        # Stop the build if there are Python syntax errors or undefined names
+        - flake8 . --count --select=E901,E999,F821,F822,F823 --ignore=E266 --show-source --statistics
+        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+        - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --ignore=E203,E266,E501,E722,F401,F403,F405,W503,C901 --statistics
+    # - name: "static type check"
+    #   script:
+    #     -  mypy pytorch_widedeep --ignore-missing-imports  --no-strict-optional
+      after_success: skip
+
 install:
   - pip install --upgrade pip
   - pip install .