Add Travis build

.travis.yml

+{
+  "language": "python",
+  "python": "2.7",
+  "install": [
+    "pip install -r requirements.txt"
+  ],
+  "script": [
+    "pytest"
+  ],
+  "group": "stable",
+  "dist": "trusty",
+  "os": "linux"
+}