sample_q: Sample transition matrix of environment process
In zhifeiyan/WeibullHM: A Gibbs Sampler of a Bayesian Weibull Hidden Markov Model

Produce a Gibbs sample of transition matrix of environment process of a subject

1	sample_q(q, et, prior, ntrial, nenv)

`q`	a matrix of current update of transition matrix of environment process
`et`	a vector of current update of environment process of a subject
`prior`	a matrix of concentration parameters of Dirichlet priors, each row corresponds to a row of transition matrix
`ntrial`	total number of trials
`nenv`	total number of environments

A list with the following components:

`q`	a Gibbs sample of transition matrix of environment process
`accept`	a binary indicator vector of acceptance or rejection of proposed sample of each row of transition matrix in the independent Metropolis–Hastings algorithm