Replace any compe support with nvim-cmp

[Julian]

nvim-compe was deprecated a bit back and replaced by nvim-cmp.

(There's also tabnine support for cmp here which may be worth trying given some success in vscode-land for Lean)

[Karthik-Dulam]

Currently the readme.md file conflicts on the recommended plugin to use.
Under "Installation"
Plug 'hrsh7th/nvim-cmp' " For LSP completion
And under "Features" and in the "Recommended configuration"

Abbreviation (unicode character) insertion, can also provide a nvim-compe source.

  abbreviations = {
    -- Set one of the following to true to enable abbreviations
    builtin = false, -- built-in expander
    compe = false, -- nvim-compe source

At the moment what is the recommended plugin to use of the two?

[gebner]

I'd use builtin = true, I wonder if we should make that the default.

[Julian]

Yeah, we should. Use the builtin expander.

[Julian]

(I'll probably remove nvim-compe support, we can decide to add an nvim-cmp source if it turns out to be useful but I have other more important things in mind before ever thinking about it.)

[Julian]

#263 should make this less confusing.