Update .travis.yml to use black instead of flake8

.travis.yml

@@ -18,11 +18,11 @@ before_install:
   - conda info -a
 install:
   - conda config --add channels conda-forge
-  - conda create -q -n test-environment python=$TRAVIS_PYTHON_VERSION obspy pycurl flake8 pytest pytest-cov webtest
+  - conda create -q -n test-environment python=$TRAVIS_PYTHON_VERSION obspy pycurl black pytest pytest-cov webtest
   - source activate test-environment
   - pip install authlib flask flask-login flask-migrate flask-session flask-sqlalchemy psycopg2-binary
 script:
-  - flake8 --config=.flake8 bin/ geomagio/ test/
+  - black --check .
   - pytest
 after_success:
   - bash <(curl -s https://codecov.io/bash)