(triangulation) make method for finding initial simplex part of the triangulation class

The following discussion from !68 (merged) should be addressed:

• @jbweston started a discussion: (+1 comment)

  Could you explain what this function is meant to do?

  The comment about taking a "random" (arbitrary) simplex does not seem to fit with the function name that says that we are finding the "initial simplex".

  What is an "initial" simplex? Would it be correct to say that this finds an arbitrary simplex among the provided points? Does this simplex have to come from a delaunay triangulation, or is that an implementation detail?