[#170] Refactor MailHandler to support a default dispatch method

Contributed by Yuki Sonoda

app/models/mail_handler.rb

@@ -100,7 +100,7 @@ class MailHandler < ActionMailer::Base
     elsif m = email.subject.match(MESSAGE_REPLY_SUBJECT_RE)
       receive_message_reply(m[1].to_i)
     else
-      receive_issue
+      dispatch_to_default
     end
   rescue ActiveRecord::RecordInvalid => e
     # TODO: send a email to the user
@@ -114,6 +114,10 @@ class MailHandler < ActionMailer::Base
     false
   end
 
+  def dispatch_to_default
+    receive_issue
+  end
+  
   # Creates a new issue
   def receive_issue
     project = target_project