Fixed another regex problem

Author: danielwaterworth

lib/pusher/channel.rb

@@ -170,7 +170,7 @@ def authenticate(socket_id, custom_data = nil)
     private
 
     def validate_socket_id(socket_id)
-      unless socket_id && /^\d+\.\d+$/.match(socket_id)
+      unless socket_id && /\A\d+\.\d+\z/.match(socket_id)
         raise Pusher::Error, "Invalid socket ID #{socket_id.inspect}"
       end
     end