added travis config

travis.yml

+sudo: required
+dist: trusty
+
+language: python
+python:
+    - 3.5
+    - nightly
+
+services:
+  - docker
+
+before_install:
+  - docker pull leifurhauks/gremlin-server-tinkergraph
+
+install:
+  - pip install -r requirements.txt
+  - docker run -d --name gst -p 8182:8182 leifurhauks/gremlin-server-tinkergraph
+
+before_script:
+  - sleep 30
+
+script:
+  - python setup.py test