Optimise function calls in built-in algorithms

[saxarona]

Right now, algorithms use the code almost verbatim—as presented in Kochenderfer's book. However, there a few improvements that can be made regarding function calls.

As an example, the old version of the GA algorithms had an additional step in which the function was evaluated at the end to find the optimum before reporting it. This would extract the index in the population. To return the fitness, the function was evaluated again on that individual, as the fitness was not being saved. This resulted in an extra call.

We solved it by using the findmin function, which allowed us to return both the minimum and its index. In this way we make 1 fewer call.

Is it worth it if it's just 1 fewer call? Yes, because maybe each evaluation takes a million seconds to complete. We want to keep it at minimum.

[saxarona]

Closing this one as we continue in a project now. See updates in #60