Add some vim keybindings

[Vilhelm-Ian]

1. When I open a certain album I want to be able to press v and select multiple songs at once so I can press l so they will be added to the playlist. Also it should be able to be non continous. So I can select songs that are not one after another. Here is an example how it would work.
   vjvjjl

[ x] song1.mp3
[x ] song2.mp3
[ ] song3.mp3
[ x] song4.mp3
[ x] song5.mp3

the songs with an x will be added to playlist

2. It would be nice to be able to press / key in the key list Ctrl+h so I can find the command of a shortcut faster

[tramhao]

Great ideas!
I'll keep this in mind. Currently we're focusing fixing all bugs we found and release 0.8. After that, we could work on these new features. Thanks!