Use Travis CI to run automatic flake8 tests on PRs

If the owner of the this repo goes to https://travis-ci.org/profile and flips the repository switch __on__ then this file will enable Travis Continuous Integration to run free, automated flake8 tests on each pull request.  These tests will find syntax errors and undefined names prior to the code being reviewed.

.travis.yml

@@ -0,0 +1,23 @@
+language: python
+cache: pip
+python:
+    - 3.6
+    #- nightly
+    #- pypy3
+matrix:
+    allow_failures:
+        - python: nightly
+        - python: pypy3
+install:
+    #- pip install -r requirements.txt
+    - pip install flake8  # pytest  # add another testing frameworks later
+before_script:
+    # stop the build if there are Python syntax errors or undefined names
+    - flake8 . --count --select=E901,E999,F821,F822,F823 --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 --statistics
+script:
+    - true  # pytest --capture=sys  # add other tests here
+notifications:
+    on_success: change
+    on_failure: change  # `always` will be the setting once code changes slow down