Update PermissionScope.swift
Update PermissionScope.swift

Fixed https://github.com/nickoneill/PermissionScope/issues/114 where callback was not being called on main thread.
kylejm/PermissionScope,nickoneill/PermissionScope,kylejm/PermissionScope,felix-dumit/PermissionScope,nickoneill/PermissionScope,felix-dumit/PermissionScope