Introductory, model family, benchmarks, and technical specification vignettes

[jolars]

This pull request adds three vignettes to the package and updates one:

• A brief introductory vignette featuring a short example of fitting, plotting and predicting.
• The benchmarks vignette has been updated with results based on running simulations on an amazon ec2 server. It now features benchmarks from all of the current families (gaussian, binomial and multinomial). Note that the results from the gaussian model are nonsensical at the moment. I believe that this is because the package isn't at all optimized for dense problems. These benchmarks will be updated before release.
• A technical documentation featuring pseudocode for the algorithm and descriptions of the various preprocessing steps.
• A vignette for the various model families, featuring an example for each one.

These are still a work in progress so I don't expect to merge this one right now, but I'd love for you to pitch in if you have any feedback.

Edit (18/13/8)

I have now also generated a pkgdown-site for the project, which I intend to link to as the final work product of gsoc.

[michaelweylandt]

This is a good start - I only reviewed the vignettes since I think the other changes are already under review as #15. I particularly appreciated the technical write up - I finally (sort of) get the point of the lagged update structure.

[michaelweylandt]

Did you want another round of comments on this?

[jolars]

Hm, thanks but let's wait a little. I noticed that I had missed seeing to a couple of your comments too.

[jolars]

I'll merge this one in now and upload the pkgdown site.