travis: Add pypy3 to envlist

.travis.yml

@@ -1,13 +1,20 @@
 sudo: false
 language: python
-python: "2.7"
+python: "3.4"
+env:
+    - TOX_ENV=py26
+    - TOX_ENV=py27
+    - TOX_ENV=py33
+    - TOX_ENV=py34
+    - TOX_ENV=pypy
+    - TOX_ENV=pypy3
 
 install:
-    - pip install -M tox
+    - pip install -U tox
 
 before_script:
     - "mysql -e 'create database test_pymysql  DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;'"
     - "mysql -e 'create database test_pymysql2 DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;'"
     - cp .travis.databases.json pymysql/tests/databases.json
 
-script: tox
+script: tox -e $TOX_ENV

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,py33,py34,pypy
+envlist = py26,py27,py33,py34,pypy,pypy3
 
 [testenv]
 commands = ./runtests.py