[SPARK-2182] Scalastyle rule blocking non ascii characters.

...erators.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #2358 from ScrapCodes/scalastyle-unicode and squashes the following commits:

12a20f2 [Prashant Sharma] [SPARK-2182] Scalastyle rule blocking (non keyboard typeable) unicode operators.