update k2pdfopt to version 1.64a
Merge pull request #729 from chrox/new_ui_code

update k2pdfopt to version 1.64a
add toggle switch widget in config option
Merge branch 'new_ui_code' of git://github.com/hwhw/kindlepdfviewer into new_ui_code
Merge pull request #730 from chrox/toggle_switch

add toggle switch widget in config option
Merge branch 'new_ui_code' of git://github.com/hwhw/kindlepdfviewer into new_ui_code