Move ScriptTransformation into the appropriate place.

Author: Reynold Xin <rxin@apache.org>

Closes #1162 from rxin/script and squashes the following commits:

2c836b9 [Reynold Xin] Move ScriptTransformation into the appropriate place.

(cherry picked from commit d4c7572dba1be49e55ceb38713652e5bcf485be8)
Signed-off-by: Reynold Xin <rxin@apache.org>