Lab: HMM State Estimation

Understand how to implement forward-backward algorithm for HMM state
estimation.
Lab: Principal Component Analysis

Understand the basics of principal component analysis
add lab to Vol3
fix image filenames
add hmmstates and fix compile issue
Merge branch 'PCA' of git://github.com/ayr0/numerical_computing into ayr0-PCA
Merge branch 'hmmstates' of git://github.com/ayr0/numerical_computing into ayr0-hmmstates