[SPARK-15207][BUILD] Use Travis CI for Java Linter and JDK7/8 compilation test

## What changes were proposed in this pull request?

Currently, Java Linter is disabled in Jenkins tests.

https://github.com/apache/spark/blob/master/dev/run-tests.py#L554

However, as of today, Spark has 721 java files with 97362 code (without blank/comments). It's about 1/3 of Scala.
```
--------------------------------------------------------------------------------
Language                      files          blank        comment           code
--------------------------------------------------------------------------------
Scala                          2353          62819         124060         318747
Java                            721          18617          23314          97362
```

This PR aims to take advantage of Travis CI to handle the following static analysis by adding a single file, `.travis.yml` without any additional burden on the existing servers.

- Java Linter
- JDK7/JDK8 maven compile

Note that this PR does not propose to remove some of the above work items from the Jenkins. It's possible, but we need to observe the Travis CI stability for a while. The main goal of this issue is to remove committer's overhead on linter-related PRs (the original PR and the fixation PR).

## How was this patch tested?

Pass the Travis CI tests. Please see the following link.

https://travis-ci.org/dongjoon-hyun/spark/builds/128595350
https://travis-ci.org/dongjoon-hyun/spark/builds/128708372

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12980 from dongjoon-hyun/SPARK-15207.

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