Improve example dependency tree

"events" might be misunderstood as the events that are sent around in
the game. Meant was a library similar to the one I made for my packman
game. (https://github.com/shak-mar/cpp-games/tree/master/library/events)
I instead use a "geometry" library for my example, which is probably
understood as more general.
Fix missing binary folder bug

When the binary folder was missing, for example because git doesn't
track empty folders, the compiler would fail to produce the output file
in there. Now, it will create the binary folder for you.
Change example in README.md as well

In aaf87da63b2308830a206ee28c3c22becbb216c5 , I changed the example in
.build/config.py already, so it needs to be corrected here.
Merge in changes of the build setup

The binary folder bug was found in this repository.