Use BootTidal.hs that ships with library

[yaxu]

Rather than shipping a BootTidal.hs of its own, the emacs plugin finds the path to the BootTidal.hs that comes with tidal itself: https://github.com/tidalcycles/Tidal/blob/master/tidal.el#L60

I think this is a good default behaviour as it means that the default boot will always work. Currently if you upgrade the plugin but not the library (or vice-versa), you'll get confusing errors.