Holistic normalization, feat selection, dimreduction, (iterative) lsi implementation

[immanuelazn]

Meta-PR that describes the culmination of efforts of multiple features.

Included and previously described features:

• Iterative LSI design docs ([r] add iterative lsi design docs #167)
• Log, tf-idf normalization functions ([r] add tf-idf and log normalization functions #168)
• Feature selection by variance, dispersion, mean accessibility ([r] Add feature selection methods by variance, dispersion, and mean accessibility #169)
• LSI, var feature selection ([r] add lsi, var feature selection #156)
• Rewrite of LSI to utilize normalizations ([r] Rewrite LSI/binned feature selection to utilize new normalization functions, add DimReduction S3 Class #181)
• Current efforts of iterative LSI