Simplify dispatcher

All we need is subscriber responding to `call` method.
Therefore, passing class is not allowed anymore. It either has to be
class instance or something that evaluates to class instance.

Author: lukaszreszke

ruby_event_store/lib/ruby_event_store/dispatcher.rb

@@ -3,18 +3,11 @@
 module RubyEventStore
   class Dispatcher
     def call(subscriber, event, _)
-      subscriber = subscriber.new if Class === subscriber
       subscriber.call(event)
     end
 
     def verify(subscriber)
-      begin
-        subscriber_instance = Class === subscriber ? subscriber.new : subscriber
-      rescue ArgumentError
-        false
-      else
-        subscriber_instance.respond_to?(:call)
-      end
+      subscriber.respond_to?(:call)
     end
   end
 end

ruby_event_store/spec/dispatcher_spec.rb

@@ -38,11 +38,11 @@ def call; end
     specify "calls subscribed class" do
       expect(HandlerClass).to receive(:new).and_return(handler)
       expect(handler).to receive(:call).with(event)
-      Dispatcher.new.call(HandlerClass, event, record)
+      Dispatcher.new.call(-> (event) { HandlerClass.new.call(event) }, event, record)
     end
 
     specify "allows callable classes and instances" do
-      expect(Dispatcher.new.verify(HandlerClass)).to eq(true)
+      expect(Dispatcher.new.verify(-> { HandlerClass.new })).to eq(true)
       expect(Dispatcher.new.verify(HandlerClass.new)).to eq(true)
       expect(Dispatcher.new.verify(Proc.new { "yo" })).to eq(true)
     end