Vim/Neovim: vim-racer shows documentation, nvim-cm-racer > YouCompleteMe, lldb.nvim does solid debugging

[zrhoffman]

For both Vim and Neovim, vim-racer does documentation "tooltips" (opens a documentation pane).

Neovim only:

• roxma/nvim-cm-racer (relies on nvim-completion-manager, which is unmaintained as of 2018-04-18) is superior to YouCompleteMe for autocompletion.
• dbgx/lldb.nvim (unmaintained as of 2018-03-11) is a good debugging experience.

Because Neovim surpasses Vim in a few areas for Rust, namely for debugging (Vim has Conque-GDB but it is very buggy), the Vim section should be dedicated to both Vim and Neovim. As of a6d98df74a, all of the plugins listed that run on Vim also run on Neovim. The Neovim-only plugins can be listed on a separate line.