fix some links to wiki pages
replaced some content with links to wiki pages

These sections now migrated to wiki pages:
- Registering `.bit` domains and identities
- How do I run my own DNSChain server?
Also fragment anchor links moved to before targets.
removed book emoji from top section of links
add @zancas to contributors list, closes #56
moved overflow content to /docs to avoid separate wiki repo
resolving merge conflict README file, wikify branch