Refactor travis.yml into stages and add travis-tox

.travis.yml

@@ -1,39 +1,40 @@
 language: python
 dist: xenial
 
-matrix:
-  include:
-    - env: TOXENV=py27
-      python: 2.7
-    - env: TOXENV=py35
-      python: 3.5
-    - env: TOXENV=py36
-      python: 3.6
-    - env: TOXENV=py37
-      python: 3.7
-      dist: xenial
-      sudo: true
-    - env: TOXENV=pypy
-      python: pypy
-    - env: TOXENV=pre-commit
-      python: 3.6
-    - env: TOXENV=mypy
-      python: 3.6
+python:
+  - "2.6"
+  - "2.7"
+  - "3.5"
+  - "3.6"
+  - "3.7"
+  - "pypy3"
 
 install:
-  - pip install tox
-
+  - pip install tox tox-travis
 script: tox
-
 after_success:
   - pip install coveralls
   - coveralls
-
 cache:
   directories:
     - $HOME/.cache/pip
     - $HOME/.cache/pre-commit
 
+stages:
+  - test
+  - name: deploy
+    if: tag IS present
+
+jobs:
+  fast_finish: true
+  include:
+    - env: TOXENV=pre-commit
+      python: 3.7
+    - env: TOXENV=mypy
+      python: 3.7
+    - stage: deploy
+      python: 3.7
+      after_success: true
       deploy:
         provider: pypi
         user: syrusakbary