Split the README and create TODO and PLAN files

[rjc]

README is overly long and it'll only keep on growing.
Created separate TODO and PLAN files and move the relevant content there.

[naufraghi]

Can we perhaps put a link here to the moved sections?

[wmanley]

For what it's worth I really like the README as it is. It immediately gives one a sense of the status of the project and the motivation for its existence. Had the README just consisted of

git-rs

Implementing git in rust for fun and education!

This is actually my second stab at it, so big blocks will land in place from my first attempt. I'm trying again this year after reading more of "Programming Rust" (Blandy, Orendorff).

I don't think the project would have caught my attention.

[rjc]

@wmanley I'm not claiming it should only contain that part - README certainly needs expanding. I'm merely proposing splitting it into files where the relevant information fits better, IMVHO.