Add 5 classifiers for fixations - IVT, IMST, KF, HMM, and I2MC

[hatran22]

We just added 5 classifiers into a new file called Classifier.py. Each classifier is contained within a class. We also modify the emip-toolkit.py to take in different classifiers per the user preference. Test code for IMST and illustration using a notebook is under construction!

• IMST and IVT basically work - can be demonstrated via unit test (IVT) or a notebook illustration of the algorithm (IMST)
• KF is assumed to work under unit test