Less known data structures

Warning

This is a DRAFT! WIP! Prior to even alpha version.

I wanted:

to learn about data structures
in small steps (one per day)
for it to be interesting
and try out GitBook

Later I may add the chapter about most popular data structure, since it’s just so frequent and known and - well - good. But that comes later. And since if I do, I need to remove this, here we are, the first TODO marker.