Fix: MarkovChain.simulate

[oyamad]

• Address Arellano_solutions migration to matplotlib 1.4.3 in python 3.4 #190: Check that init is an instance of numbers.Integral
• Check that init is in {0, ..., n-1} or {-n, ..., -1}

[mmcky]

@oyamad Thanks for this. Notebooks are now running in my py34 env

Additional notebooks have started to be written based on this excellent addition to the library. FYI - If you ever want to test additions to markov over all notebooks in the repository - this can now be done using python scripts/test-solutions.py and that will provide you with a small report.