Fix all the broken links in README.md

With many thanks to @spudbean for spotting this! <3
Moar links fixed.

Gotta catch 'em all.
Merge pull request #59 from pjf/fix_readme

Fix all the broken links in README.md
Update README with releases, contributor's guide, and more.
Flipped licenses to the Debian spec.

With some minor tweaks to remain sane.

Closes #21.
Merge pull request #63 from pjf/21_licenses

Flipped licenses to the Debian spec.
Added relationship resolution logic.

Part of #32.

Looks like it's mostly working. Will have to remove some diagnostics
from here, and have discovered bugs in the installer which need fixing.
Fix ModuleInstaller to make moar directories.

Because apparently we can't trust zipfiles to contain them
reliably.
Added CKAN.User.YesNo() for prompting users.
Prompt the user before installing a million mods.
Removed the world's least informative debugging statement.
Registry.LatestAvailable() now throws ModuleNotFoundException
Added cmdline options to control relationships on install.