Merge branch 'releases/2.1.1'

Ready for 2.1.1 release
Merge branch 'hotfix/learn'

Fix apidoc link
Add social icons to footer and fixes some stylesheets

- Add icons for Github, Twitter und Feed to footer
- Github ribbon now only on homepage
- Fixes links in about and participate page
- Fixes some stylesheets for manual and hyperlinks
Merge branch 'feature/social-icons' of git://github.com/froschdesign/zf-web into hotfix/77
Add blog feed, fixes URLs and compiled CSS added
Merge branch 'feature/social-icons' of git://github.com/froschdesign/zf-web into hotfix/77
Merge branch 'hotfix/77' into develop

Forward port #77