#19 Update threading for use with glib >=2.42

[fuesika]

Updating glib past version 2.42 will make the gui fail to start due to changes in threading that have been on hold since glib 2.22 or so, cf. the same issue at another project: https://github.com/rabbitvcs/rabbitvcs/issues/59

The problematic line is

gtk.gdk.threads_init()
prior to calling main. The solution is to remove this line. I did test this and found it to be working with both glib 2.40 as well as glib 2.42.