Republish content with pelican 3.3

Upgrade to pelican 3.3 and run (issue #31) No settings, content or css
changed.

Changes:
* Different indentation
* Footnotes no longer in index (fixes
https://github.com/peterdesmet/spoonbill/issues/15)
* Posts on author page are sorted by date (issue #24)
* Static content no longer written to /static but in root
* Authors page
Add setting OUTPUT_RETENTION

In case I use DELETE_OUTPUT_DIRECTORY
Remove footnote css
Setting SUMMARY_MAX_LENGTH to 0 (fixed #23)
Merge pull request #33 from peterdesmet/pelican3.3

Upgrade to Pelican 3.3