Implement check() function in HSMM class

[poypoyan]

The function check() in HSMM class checks model parameters for errors before performing the main algorithms.

For the HSMM (base) class, here are some of the properties to be checked:

• n_states should be at least 2, while n_durations should be at least 1.
• every entries (probabilities) in HSMM.pi, HSMM.tmat, and HSMM.dur should be greater than 0, because EM algorithm cannot update 0 probability.
• for HSMM.pi (start probabilities), numpy.shape = (n_states), and the sum should be 1.
• for HSMM.tmat (transition matrix), numpy.shape = (n_states, n_states), every diagonal is zero, and every row should add up to 1.
• for HSMM.dur (duration probabilities), numpy.shape = (n_states, n_durations), and every row should add up to 1.

For Gaussian sub-class, here are the properties:

• for GaussianHSMM.means, numpy.shape = (n_states).
• for GaussianHSMM.sdev, numpy.shape = (n_states), and all entries should be greater than 0.

Just comment if some properties are not listed here.

[poypoyan]

Update (12-Jul-2020): Implemented for both HSMM (base class) and GaussianHSMM.