Updated CHANGELOG.md to match new template

See https://github.com/symfony-cmf/symfony-cmf/wiki/Change-log-format
2.3+ compatibility
Initial german translation
Merge pull request #68 from KingCrunch/initial-german

Initial german translation
loosen BlockBundle dependency

fixes #59
adjust to container block refactoring
corrected link to docs
Merge pull request #70 from shieldo/patch-1

corrected link to docs