add default savefig directory
call self.update() instead of self.repaint() seems to draw faster and with less flicker for qt4agg
replace tabs with spaces
explicitly missing key or empty str signals to use cwd
PEP8
Implement savefig.directory for tk gui
fix comment in gtk FileChooserDialog: does *not* remember last selected file/directory
Implement savefig.directory for gtk gui
Implement savefig.directory for gtk3 gui
update CHANGELOG with savefig.directory feature