Make PropertySortOrder lint message more useful

Tells you what order it was expecting for the properties. Great for
custom orders, so we don't have to compare the order and our SCSS.

Closes #270.

Change-Id: I0875ce4751cbbf4f076c4b98e3e1c03b84c4636f
Reviewed-on: http://gerrit.causes.com/43723
Reviewed-by: Joe Lencioni <joe.lencioni@brigade.com>
Tested-by: Joe Lencioni <joe.lencioni@brigade.com>