## What changes were proposed in this pull request?
We are currently detecting the changes in `R/` directory only and then trigger AppVeyor tests.
It seems we need to tests when there are Scala codes dedicated for R in `core/src/main/scala/org/apache/spark/api/r/`, `sql/core/src/main/scala/org/apache/spark/sql/api/r/` and `mllib/src/main/scala/org/apache/spark/ml/r/` too.
This will enables the tests, for example, for SPARK-20088.
## How was this patch tested?
Tests with manually created PRs.
- Changes in `sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala` https://github.com/spark-test/spark/pull/13
- Changes in `core/src/main/scala/org/apache/spark/api/r/SerDe.scala` https://github.com/spark-test/spark/pull/12
- Changes in `README.md` https://github.com/spark-test/spark/pull/14
Author: hyukjinkwon <gurwls223@gmail.com>
Closes#17427 from HyukjinKwon/SPARK-20092.
## What changes were proposed in this pull request?
- Remove support for Hadoop 2.5 and earlier
- Remove reflection and code constructs only needed to support multiple versions at once
- Update docs to reflect newer versions
- Remove older versions' builds and profiles.
## How was this patch tested?
Existing tests
Author: Sean Owen <sowen@cloudera.com>
Closes#16810 from srowen/SPARK-19464.