add TravisCI config

Author: json2d

.travis.yml

@@ -0,0 +1,16 @@
+language: python
+python:
+  - "2.7"
+  - "3.4"
+  - "3.5"
+  - "3.6"      # current default Python on Travis CI
+  - "3.7"
+  - "3.8"
+  - "3.8-dev"  # 3.8 development branch
+  - "nightly"  # nightly build
+# command to install dependencies
+install:
+  - pip install -r requirements.txt
+# command to run tests
+script:
+  - python tests/units.py