README intro mentions statelessness
DESCRIPTION moved after EXAMPLE, add HOW DOES THIS WORK before
Shoehorn in summary of problem with git-subtree merge

I thought of this phrasing when trying to summarize git-subtree to David
Rieman, don't feel like fully revising COMPARISON WITH GIT-SUBTREE
(which is already a little repetitive), but wanted to work in the
phrasing somewhere.