PCA cookbook is out of date

[isaacovercast]

The pca cookbook is really nice, but there are a couple things that are outdated.

• comps, var = pca.run() - run() doesn't return these anymore, it stores them inside the pca object as pcaxes and variances
• pca.run_tsne() - The TSNE section of the cookbook does it by hand but we have a function to do this now which is not documented here (also run_umap()).