Add convenient methods to IO class.

io_bin.rb

class IO
    def readb; return self.read(1).unpack("C")[0]; end
    def readw; return self.read(2).unpack("v")[0]; end
    def readl; return self.read(4).unpack("V")[0]; end
    def readbw; return self.read(2).unpack("n")[0]; end
    def readbl; return self.read(4).unpack("N")[0]; end
end