moved init of object variables from prototype to init function so we can have more than one mpdsocket object at a time
slight tweak to this.version
added support for unix domain sockets
THIS BREAKS BACKWARDS COMPATABILITY: all responses are now returned as an array
  there is a section you can uncomment to restore backwards compatability
refactored how response data from mpd is handled:
  sometimes big responses are not entirely contained in a single read
  cycle, so bufferData receives data until an end of line is seen and
  sends that complete line to handleLine. handleLine chuncks up the
  potentially multiple-line response and passes the complete response
  to handleLines which processes the response
extract error message based on location of '}' in the response
handle responses that might have the same attributes repeated several times (like genre)