Added missing dependency :logger application dependency

[edescourtis]

In some cases :libring was started before :logger causing errors like:

=INFO REPORT==== 15-Oct-2018::21:41:03 ===
    application: libring
    exited: {bad_return,
                {{'Elixir.HashRing.App',start,[normal,[]]},
                 {'EXIT',
                     {#{'__exception__' => true,
                        '__struct__' => 'Elixir.RuntimeError',
                        message =>
                            <<"cannot use Logger, the :logger application is not running">>},
                      [{'Elixir.Logger.Config','__data__',0,
                           [{file,"lib/logger/config.ex"},{line,53}]},

[bitwalker]

Thanks!