travis change

.travis.yml

@@ -3,15 +3,10 @@ python:
   - "3.4"
   - "3.5"
   - "3.6"
-matrix:
-  include:
-    - python: 3.7
-      dist: xenial
-      sudo: true
+  - "3.7"
 install:
   - pip install coveralls
   - pip install codecov
-  - pip install pyyaml
   - pip install vcrpy
   - pip install -r requirements.txt
   - python setup.py install