Updated .travis.yml

.travis.yml

@@ -1,20 +1,16 @@
-dist: trusty
-sudo: false
-
-language: python
-matrix:
-  include:
-    - python: 2.7
-    - python: 3.4
-    - python: 3.5
-    - python: 3.6
-    - python: 3.7
 dist: xenial
-      sudo: true
+language: python
+
+python:
+  - "2.7"
+  - "3.4"
+  - "3.5"
+  - "3.6"
+  - "3.7"
 
 install:
   - pip install -r requirements.txt
-  - pip install pytest==3.8.0 pytest-cov==2.6.0 codecov flake8
+  - pip install pytest pytest-cov codecov flake8
   - if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then pip install mock; fi
 
 script: