Use commands instead of functions

[KabbAmine]

Hi.

First of all, thanks for your awesome work, livedown is really nice :smiley:

I'm not a vimscript expert but there are some advices and also explanations of my PR:

• Always use ! with command to avoid errors when resourcing a vim script containing the same command (Your vimrc for example).
• For a common use, vim commands are better than functions when you want to map them.

English not being my mother tongue, I could have made some spelling errors in the README, check it if you want.

[shime]

Thanks! :heart: