update travis again

Author: OrderAndCh4oS

.travis.yml

@@ -3,13 +3,11 @@ python:
   - "3.4"
   - "3.5"
   - "3.6"
-before_install:
+  - "3.7"
+install:
   - pip install --upgrade pip
   - pip install poetry
   - poetry install -v
-# command to install dependencies
-install:
-  - pip install -U -r requirements.txt
 # command to run tests
 script:
   - coverage run -m pytest