Support $VCSH_GITIGNORE == none

This will neither add core.excludesfile nor write a ignore file.
Update README.md

* Add 30 second overview
* Make GitHub parse intra-document MarkDown links
  Sadly, the MarkDown specs are missing this feature
doc/vcsh.1.ronn: Use new tagline
README.md: Better wording
README.md: %s/</`/gc; %s/>/`/gc
README.md: Better wording
README.md: Move Contact section to the end
README.md: Better wording
PACKAGING.md: Major rewrite
README.md: Rewrite Introduction
README.md: Move Introduction to beginning
README.md: Improve 30 second overview
README.md: Improve 30 second overview
README.md: Move 'Talks' back into 'Intorudction'
README.md: Remove trailing hashes from section headers
Yet another new tagline
README.md: Update Overview
Fix [mr] links
README.md: Fix mistake & improve sample code
README.md: More usage examples