Streams a file over a given connection. Streaming begins once the object is instantiated. Typically FileStreamer instances are not reused.

Streaming uses buffering for files larger than 16K and uses so-called fast file reader (a C++ extension) if available (it is part of eventmachine gem itself).

@example

 module FileSender
   def post_init
     streamer = EventMachine::FileStreamer.new(self, '/tmp/bigfile.tar')
     streamer.callback{
       # file was sent successfully
       close_connection_after_writing
     }
   end
 end

@author Francis Cianfrocca