configure travis-ci to run pylint

.travis.yml

@@ -0,0 +1,19 @@
+language: python
+
+python:
+- 3.6
+- 3.6-dev
+- 3.7
+- 3.7-dev
+
+# required for python >= 3.7
+dist: xenial
+
+install:
+- pip install pipenv
+- pipenv sync --dev
+- pipenv graph
+
+script:
+- pipenv run pylint free_disk
+# - pipenv run pytest