Set Coxian Structure

Assigns random values for the hidden state transition matrix, A, the symbol emission probability matrix, B, and the initial state probability vector, pi, satisfying the stochastic constrains, but sets the Markov chain to a coxian structure.

Usage: set_coxian($<$N$>$, $<$M$>$)

where $<$N$>$ is the number of hidden states; and $<$M$>$ is the number of observation symbols of the hmm model.