Check sort order of properties in media query blocks

The `PropertySortOrder` linter was not linting properties within media
query blocks. Fix by adding a simple `alias_method` of `visit_media` to
`check_sort_order`.

Change-Id: I32bea628d257a6032add4f0a174ab0e80466f4ee
Reviewed-on: http://gerrit.causes.com/42989
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>