SpellBad undercurl not working in all terminals

[idnsunset]

First thanks for making these awesome color schemes. I run into some trivial problems when running Vim in xterm.

The SpellBad highlighting to:

hi SpellBad guifg=NONE guibg=NONE gui=undercurl ctermfg=NONE ctermbg=NONE cterm=undercurl

However, not all terminals support undercurl, in xterm the badly spelled words are not styled distinctly. it would be better to set a ctermbg or ctermfg for it.

[lunacookies]

Would it be better to make them red, too?

[idnsunset]

I personally prefer to set spellCap, spellBad, spellLocal and spellRare to different colors, just like what's done in Gui.

[lunacookies]

I haven’t used Vim since June of last year, so I don’t really have the motivation to choose some good colour combinations for these. If you have the time would you mind creating a PR? If you do, don’t forget to edit the templates and not the generated colour scheme files themselves.