change Travis-CI config

.travis.yml

@@ -1,12 +1,12 @@
 language: python
 python:
-  - "3.5"
+  - "3.6"
 services:
   - mongodb
 # command to install dependencies
 install:
-  - pip install -U setuptools pip
-  - python setup.py develop
+  - pip install -r requirements.txt
+  - pip install -r requirements-test.txt
   - pip install coveralls
 # command to run tests
 script: ./runtests.sh