Add mysql tests

.travis.yml

@@ -4,7 +4,7 @@ sudo: false
 language: php
 
 services:
-  # - mysql
+  - mysql
   - postgresql
 
 addons:
@@ -21,7 +21,7 @@ before_install:
   - phpenv config-add travisphp.ini
   - psql -c 'create database testing;' -U postgres
   - psql -U postgres -c "create extension postgis"
-  # - mysql -e 'CREATE DATABASE testing;'
+  - mysql -e 'CREATE DATABASE testing;'
   - cp tests/Config.php.travis tests/Config.php
 
 script: