Update .travis.yml

Re #348   - did you try it like this?

.travis.yml

@@ -1,10 +1,10 @@
 language: python
-python:
+
-  - "3.6"
+python: "3.6"
-install:
+
-  - cd config
+install: pip3 install homeassistant
-  - pip3 install homeassistant
+
-script:
+script: hass -c config/ --script check_config
-  - hass -c . --script check_config
+
 before_install:
   - mv config/travis_secrets.yaml config/secrets.yaml