[SPARK-1105] fix site scala version error in docs

https://spark-project.atlassian.net/browse/SPARK-1105

fix site scala version error

Author: CodingCat <zhunansjtu@gmail.com>

Closes #618 from CodingCat/doc_version and squashes the following commits:

39bb8aa [CodingCat] more fixes
65bedb0 [CodingCat] fix site scala version error in doc
(cherry picked from commit 7b012c93973201a1cbb4fc9a02e322152e5185a9)

Conflicts:

	docs/_config.yml