Fix some wording in README

1. Spelling fix
2. Awkward wording in the GfW & GfM note
Add links to variant repos and remove languages that never took off.
Merge pull request #37 from parkr/patch-1

Fix some wording in README
Merge pull request #34 from nschonni/prose-patch-2

Add links to variant repos and remove languages that never took off.
Use GitHub release page instead of the Wiki