Markdown needs to be >2.2.0 due to 2.1.1 headerid extension tested broken with…

Markdown needs to be >2.2.0 due to 2.1.1 headerid extension tested broken with newer ElemenTree versions

requirements.txt

 django>=1.4
 South
-Markdown<2.3.0
+Markdown>2.2.0
 django-sekizai<0.7
 django-mptt>=0.5.3
 sorl-thumbnail