removed unused var and lack of parens to get rid of warning

When loading the gem with `$VERBOSE = true` some errors are thrown:

     pry(main)> require 'ruby-mpd'
    /home/michael/.rvm/gems/ruby-2.0.0-p353/gems/ruby-mpd-0.3.1/lib/ruby-mpd.rb:98: warning: `*' interpreted as argument prefix
    /home/michael/.rvm/gems/ruby-2.0.0-p353/gems/ruby-mpd-0.3.1/lib/ruby-mpd/parser.rb:124: warning: assigned but unused variable - chunks

This PR makes minor changes to that these warnings aren't triggered.

http://devblog.avdi.org/2011/06/23/how-ruby-helps-you-fix-your-broken-code/