add new movement command

[sutrisnob45]

try to fix #240
aaab23c basically just a simple hack

[gokcehan]

@sutrisnob45 Commands next_parent and prev_parent can be implemented as custom commands as such:

map N :updir; down; open
map P :updir; up; open

So I don't think we should have them as builtins.

Command goto should probably be merged with top or bottom somehow so that we can have a default keybinding for that. @yangmillstheory wanted to be assigned to the issue so ideally I think you should coordinate to not work on the same issue at the same time.

[sutrisnob45]

got it