Fixes #139 (Shift-F5 bug) and #95 (Cmd-Alt-P feature)

1. All variables moved to top (as they used in the first three cases)
2. `slide` is now fallbacked to 0 slide (as it help in F5 and Cmd-Alt-P cases)
3. Alt-Ctrl+Cmd keys detection (to keep browser shortcuts safe) moved to cases instead of top as we need Alt+Cmd for the first case.

And it needs to be carefully reviewed of course.