wip add LDA algorithms
Created by: Eleanor2
- There are 2 new files added: lda.go and lda_test.go
- lda.go computes the linear discriminate analysis in golang
- lda.go was based on a file that computed LDA in Java: https://github.com/haifengl/smile/blob/master/core/src/main/java/smile/classification/LDA.java -lda_test.go tests lda.go with sample data