Update .travis.yml
Update .travis.yml

* Up Redmine version to 2.5.2 from 2.5.1
* Up Ruby version to 2.1.3 from 2.1.2
* Add Ruby 2.2.0-preview1

pinzolo/redmine_persist_wfmt,pinzolo/redmine_persist_wfmt,pinzolo/redmine_persist_wfmt