travis: Use `./gradlew check` instead of `./gradlew test` for testing
travis: Use `./gradlew check` instead of `./gradlew test` for testing

Because `./gradlew check` invokes `checkstyle` and `findbugs` in
before testing.
`./gradlew test` invokes only test task.
We can find out more issues than using `./gradle test`.

hiroyuki-sato/embulk-parser-jsonpath,hiroyuki-sato/embulk-parser-jsonpath