v0.5.0

- excellent improvements to sections! See: 2f4650b397dbfdb476f5bc40a088e0040c051536
- add support for `piwik`, a self-hosted comments platform
- fix indentation of `li` elements
- fix list style type for `ol > li` elements (previously they always used disc instead 
  of decimal)
- upgraded highlightjs version; support for more highlightjs options 
- security improvements such as including `noopener` in links
- more social icons

commit log