Add ToggleSelectionAndSelectNext handler which executes.

I added ToggleSelectionAndSelectNext which select next line after ToggleSelection.

Percol's C-SPACE is bound to `percol.command.toggle_mark_and_next` like `ToggleSelectionAndSelectNext` by default.
If you don't mind, I think it is better to bind C-SPACE to ToggleSelectionAndSelectNext in peco too.

https://github.com/mooz/percol#selecting-multiple-candidates