Ignore SpecialGlobalVars Rubocop check

Including the `English` gem in order to silence this check doesn't seem
worthwhile.

Change-Id: Idc9789e68bc38957b520909c7efa36d92d5f6cb3
Reviewed-on: http://gerrit.causes.com/36002
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>