Synchronize .travis.yml with upstream moodle-plugin-ci, fix broken MySQL builds

.travis.yml

 language: php
 
-# Workaround for fixing that Selenium server is not running and therefore Behat tests not working
-sudo: required
-# ORIGINAL:
-# sudo: false
+sudo: true
+
+services:
+  - mysql
 
 addons:
   firefox: "47.0.1"
   postgresql: "9.4"
   apt:
     packages:
-# Workaround for fixing that Java could not be downloaded from Oracle website.
       - openjdk-8-jre-headless
-# ORIGINAL:
-#     - oracle-java8-installer
-#     - oracle-java8-set-default
 
 cache:
   directories:
@@ -52,5 +48,6 @@ script:
   - moodle-plugin-ci savepoints
   - moodle-plugin-ci mustache
   - moodle-plugin-ci grunt
+  - moodle-plugin-ci phpdoc
   - moodle-plugin-ci phpunit
   - moodle-plugin-ci behat --dump