Thank Shivaram Venkataraman for your support. This is a prototype script to validate the R files.

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #6922 from yu-iskw/SPARK-6813 and squashes the following commits:

c1ffe6b [Yu ISHIKAWA] Modify to save result to a log file and add a rule to validate
5520806 [Yu ISHIKAWA] Exclude the .lintr file not to check Apache lincence
8f94680 [Yu ISHIKAWA] [SPARK-8495][SparkR] Add a `.lintr` file to validate the SparkR files and the `lint-r` script