Travis Integration

- I introduce `env` within `.travis.yml` to work easier with multiple database configuration in the future (ref : http://about.travis-ci.org/docs/user/database-setup/#Multiple-database-systems).

- I also alter the database username within config (from `root` to `travis`). The reason is because mostly, any user with `phpadmin` will be forced to set up their `root` user with a password. And for that reason, i think it is easier for them to create another passwordless user, rather than altering their `root` user which may be already used by other app. But let me know if someone think it was unnecessary and i will revert these one.