Updated Black-Litterman content

I'm slowly getting more of the Black-Litterman content from my paper converted over into webpages and putting it up on the site. Just added two more pages, cookbook which describes exactly what one needs to do to implement Black-Litterman in terms of variables and formulas, and methods which describes the differences between the papers I've worked on.

I still chase the holy grail of reproducing the results from the original paper. I've tried several approaches to the reverse optimization and just can't get crank the weights from the returns or vice versa. I guess next I need to figure out what values are off a bit in the covariance matrix, or in the weights or returns.