Change log for the gnuplot Haskell binding

0.5.7:

• Gnuplot.Terminal.QT

• Gnuplot.Execute: Do longer call pgnuplot on Windows. It is gone in gnuplot-5.0 in January 2015.

0.5.5:

• Gnuplot.Utility.quote bugfix: Do not escape printable non-ASCII characters because gnuplot has no universal escaping support for Unicode codepoints.