fix download link for dmd2 windows exe
Merge branch 'master' of github.com:D-Programming-Language/d-programming-language.org
use numbered lists in changelog
S3 download links except for OSX
Correction of request to change `immutable` fields to `immutable`.

Not sure this is a correct correction.
Merge pull request #330 from denis-sh/patch-3

Correction of request to change `immutable` fields to `immutable`.
Add docs for documented unittests.
Add link to documented unittest page to the changelog.
Merge pull request #264 from AndrejMitrovic/DocumentUnittest

Add docs for documented unittests.
Merge pull request #331 from AndrejMitrovic/AddDocumentUnittestLink

Add link to documented unittest page to the changelog.