Implement Viterbi Algorithm and a simple test case

[formulahunter]

Description of new feature, or changes

Implement Viterbi Algorithm and a simple test case

Checklist

• Your branch is up-to-date with the base branch
• You've included at least one test if this is a new feature
• All tests are passing

Related Issues and Discussions

#25

People to notify

@remes2000
@manrajgrover

[formulahunter]

The spec at the top of viterbi.js is intentionally generic -- it was written before the implementation to define the scope/requirements. Now that the implementation is finished, the spec might come across as a bit excessive. Let me know if you think it should be simplified.

The test case in testViterbi.js is very basic as there are not many constraints on the inputs, but of course I'm open to suggestions.