rename emacs-hy to hy-mode

[vhqr0]

trafficstars

I am the contributor to this piece of code, and after reviewing the entire file recently, I think that perhaps changing "emacs-hy" to "hy-mode" would be more appropriate?

Additionally, I think it might be better to provide a default formatter for all languages: copy the buffer or region, switch to the default major mode, then call indent-region/delete-trailing-whitespace, and finally merge back into the original buffer.