kfe1_clarify_unit_simplex

[shlff]

Hi @jstac , this PR adds the following wiki link to clarify unit simplex in the subsection Review of the Discrete Time Case of lecture kolmogorov_fwd:

• https://en.wikipedia.org/wiki/Simplex

[jstac]

In the link that you provided, what I called the "unit simplex" is called the "standard simplex".

Perhaps we should change "unit" to "standard" and then give the link https://en.wikipedia.org/wiki/Simplex#The_standard_simplex

[shlff]

Thanks for your suggestion, @jstac . I agreed with you that this is a better clarification and I made changes as you suggested.

[jstac]

Thanks @shlff .