Just list Python dependencies in ReadMe

Keeps all dependencies in one place. Also, no-one wants to install scipy,
scikit-* and company from source...
Add description to argument parser
Eigenface decomposition script

Eigenface decomposition produces pretty poor results, to be honest. The first
couple of eigenfaces look like "the attack of the phantoms" and it gets worse
after that with the lower-valued eigenfaces mostly looking like random noise. I
guess there's just too much variance in the data.
Tag eigenfaces with percent variance explained