Enable travis to run tests

Fixes prestodb#151.

Author: kokosing

tests/.travis.yml

@@ -0,0 +1,8 @@
+language: python
+python:
+  - "2.7"
+install: 
+  - pip install --upgrade pip==6.1.1
+  - pip install -r requirements.txt
+script: 
+  - make clean lint docs test-all