Removing Terry's (unused) example code

Projectile keeps opening them, which is bugging me.
Switching to prefix notation for formula

Apparently it is common in the GP literature to use prefix, not
postfix. I personally love postfix because of its stack-like nature. But
they're right, this is more readable.
Petty print fixes
Smaller (faster) tests
Changing division representation from / to %

It is a bit more clear. I originally thought it would be confused for
mod because C++ is in my head, but if I were to implement mod, I would
surely represent it as "mod".
Logging raw fitness as well