Truly Sigma .vimrc

SigmaVimRc started as Vim AND Neovim configuration or distribution if you will. With time it started growing, it went from pure VimScript to including some Neovim-only Lua files and started to be quite messy. It was, on one hand, limiting development of Neovim support, but also leaving Vim behind, as it was meant to maintain feature parity between both editors and Vim started becoming a second class citizen here. At some point I almost decided to drop Vim at all, but instead... I dropped Neovim and created a separate project.

I could have just removed all Neovim stuff, push and forget, but I decided to make it clean. Probably it still can be cleaner, but I think it is way better with CoC configuration being split into separate, autoloaded files instead of one big coc file, copy pasted from coc.nvim.

Also SigmaVimRc is now installed more like vim-plug (single file download that bootstraps the whole configuration), and then the whole plugin is managed by vim-plug, like any other Vim plugin.

I entertained putting ALE here, but I never used it extensively, so I decided to go with CoC instead. It's very solid solution. It only lacked proper lightline plugin (that is maintained), so I included some additional functions in Sigma to provide diagnostics. Also kyotonight.vim was updated solely for the lightline diagnostics to look better.

Hope you'll enjoy!