[Help wanted] Support Neovim

[heavenshell]

Currently Noevim does not support.
I don't have any Neovim env and knowledge.
So I'm very appricated to someone send me PR 😉

1. Vim8's use job_start. Neovim's use jobstart
2. Add Vim8's CI and Neovim's CI
   Use GitHub action and drop TravisCI