Improve Call initialization performance

Use an ActorProxy (subclass) instead of a method_missing definition on every Call.new. This considerably improves Call.new performance; benchmarks show approximately a 30-40% improvement: https://gist.github.com/kares/3576e272250204eb66d1

CHANGELOG.md

@@ -1,4 +1,5 @@
 # [develop](https://github.com/adhearsion/adhearsion)
+  * Improve Call initialization performance. Use an ActorProxy (subclass) instead of a method_missing definition on every Call.new. This considerably improves Call.new performance; benchmarks show approximately a 30-40% improvement: https://gist.github.com/kares/3576e272250204eb66d1
 
 # [2.6.0](https://github.com/adhearsion/adhearsion/compare/v2.5.4...v2.6.0) - [2015-02-01](https://rubygems.org/gems/adhearsion/versions/2.6.0)
   * Feature: `Call#after_hangup_lifetime` optionally overrides `Adhearsion.config.platform.after_hangup_lifetime` ([#537](https://github.com/adhearsion/adhearsion/pull/537))

lib/adhearsion/call.rb

@@ -16,22 +16,23 @@ class Call
     CommandTimeout  = Class.new Adhearsion::Error
     ExpiredError    = Class.new Celluloid::DeadActorError
 
+    # @private
+    class ActorProxy < Celluloid::ActorProxy
+      def method_missing(meth, *args, &block)
+        super(meth, *args, &block)
+      rescue ::Celluloid::DeadActorError
+        raise ExpiredError, "This call is expired and is no longer accessible. See http://adhearsion.com/docs/calls for further details."
+      end
+    end
+
     include Celluloid
     include HasGuardedHandlers
 
+    proxy_class Call::ActorProxy
+
     execute_block_on_receiver :register_handler, :register_tmp_handler, :register_handler_with_priority, :register_handler_with_options, :register_event_handler, :on_joined, :on_unjoined, :on_end, :execute_controller, *execute_block_on_receiver
     finalizer :finalize
 
-    def self.new(*args, &block)
-      super.tap do |proxy|
-        def proxy.method_missing(*args)
-          super
-        rescue Celluloid::DeadActorError
-          raise ExpiredError, "This call is expired and is no longer accessible. See http://adhearsion.com/docs/calls for further details."
-        end
-      end
-    end
-
     # @return [Symbol] the reason for the call ending
     attr_reader :end_reason