Document installing dependencies

@charlierudolph @allewun what do you think?
`~/.config` is the new standard where all config and dot-files should go. Many modern apps like `hub` use it as well. 

`$fish_complete_path` is an array of directories that can contain autocomplete files. Mine has 4 directories in it. I can't pick one easily from it. 

You should seriously use Fish shell, its much better than bash/zsh.