float32 vs float 64 homogeneity

[luisaforozco]

When defining variables:

trange_burn = (0.0f0, 10.0f0) # float32
dt, saveat = (1e-2, 1) #float64

We should homogenize and keep consistency.

I would suggest for the examples use float32 unless we see some precision problem arising. This would make the notebooks run faster.

[luisaforozco]

It seems that in julia Float64 is the default and there isn't a built-in way to globally change such default to Float32. Therefore, I would suggest that for the sake of clarity of the examples we keep everything in Float64. In this way we would avoid extra code for casting and warnings due to different floating-point types.