Improve open in explorer
Improve open in explorer

Fix issue on archlinux gnome.
Use a platform specific message:
  - Windows: "Show in explorer"
  - OS X: "Show in finder"
  -  Linux: "Show in Nautilus", "Show in Dolphin",...

zwadar/pyqode.core,pyQode/pyqode.core,pyQode/pyqode.core