Update .travis.yml

Author: sujitmandal

.travis.yml

@@ -1,14 +1,12 @@
 language: python
 python:
   - 2.7
-  - 3.0
   - 3.5
   - 3.6
   - 3.7
   - 3.8
+  - pypy3
 
-before_script:
-  - composer install --no-interaction
-  
+install: pip install tox-travis
 script:
-  - vendor/bin/python
+  tox