Improve neovim installation on Debian systems (particularly Raspberry Pi)

[daephx]

I would like to get the unstable branch, ie. v0.6+ installed on my raspberry pi.
Installation of neovim is currently handled with PPA packages which are only supported on Ubuntu.

I'm currently more familiar with Ubuntu and dotbot doesn't have a smart way of handling conditional
configurations for different platforms such as, arch, Debian, Ubuntu.

Perhaps Debian backports could prove helpful?