Expand the Get Involved (Zapoj se) section

Say more about the points mentioned, remove Pyvec and its sponsors.
From English version, remove the "write/translate" and "help meetup
organizers" points.
Remove the swag link (Propaguj).
Dismantle the Facts and Names section (Zorientuj se)

- Python CZ: the webpage is obvious. Twitter is inactive :(
- Pyvec: will get its own section
- Pyvo, Rubyslava: Added a short intro to meetup section instead
- Pyladies: Should go into a new section (Education?) when the time comes

Fixes https://github.com/pyvec/python.cz/issues/37
Add a Pyvec section
Remove Pilsen meetup

The date, 19. 7., started to look like we're planning half a year ahead :(
Remove links to similar web languages

I fail to see any relevance.