Added a notice for Jitpack users to the README
Added a notice for Jitpack users to the README

* related to #315, Jitpack causes an error when it tries to resolve PD's dependency itself
* users need to change the order of repositories available to their project, so that jcenter takes precedence

aurae/PermissionsDispatcher,aurae/PermissionsDispatcher,permissions-dispatcher/PermissionsDispatcher,hotchemi/PermissionsDispatcher,MaTriXy/PermissionsDispatcher,MaTriXy/PermissionsDispatcher,MaTriXy/PermissionsDispatcher,aurae/PermissionsDispatcher,hotchemi/PermissionsDispatcher,hotchemi/PermissionsDispatcher,permissions-dispatcher/PermissionsDispatcher