support python 3.4 testing

python 3.4 is not supported by any 1.4 release of mysqlclient.  Pip is
installing the 1.4.4 version even when run from python 3.4.  Check
version and install 1.3.14 on python 3.4 but newest one on all other
versions.

Author: rouilj

.travis.yml

@@ -84,7 +84,8 @@ before_install:
   - cd $TRAVIS_BUILD_DIR
 
 install:
-  - pip install mysqlclient
+  - [[ $TRAVIS_PYTHON_VERSION == "3.4"* ]] && pip install mysqlclient==1.3.14
+  - [[ $TRAVIS_PYTHON_VERSION != "3.4"* ]] && pip install mysqlclient
   - pip install psycopg2
   - pip install gpg pytz whoosh pyjwt
   - pip install pytest-cov codecov