Modernize the blog

- Update to Pelican 3.3.0 & newest plugins
  - redo static files config to work with this version
- Use Czech footer for Czech articles
- Use Markdown Downheader to pull article headings to <h2> & below
- Add a rudimentary plugin to add &nbsp; roughly as required Czech typography
- Add direct links to the articles on Github
- Add style for <code>, <h2>, <sup>, footnotes
Remove tabs everywhere
Replace "Tagged:" by a language-neutral pictogram
Add style for small screens
Use relative font sizes
Say encukou.cz instead of encukou/blog in the header
Use a more fitting icon for work
Run pngcrush on all the images
Add first 2 installments of a Python tutorial