Stop testing Python 2.7 in TravisCI

.travis.yml

@@ -11,17 +11,9 @@ script: pytest -m offline
 
 jobs:
   include:
-  - python: 2.7
-    before_install:
-    - sudo apt-get -y install python3-pip python3-setuptools
-    - sudo pip3 install flit
-    install: flit install --python python --deps production --extras test
-  - python: 3.4
   - python: 3.5
   - python: 3.6
   - python: 3.7
-    dist: xenial
-    sudo: required
   - python: pypy3.5
 
   - name: Lint