plugin/auditory.vim: Add gj & gk mappings

Map to up and down sounds.
plugin/auditory.vim: Add 0^_$g_ mappings

Add mappings for beginning and end of line that play the left and right
sounds.
plugin/auditory.vim: Add Cantina insert mode

Version of insert mode binding that maps to the Cantina song. Bits of
the song are in wav files. They get played in order on keypress in
insert mode.