Clean up figure paths in vignettes

[Andrew0Hill]

This PR addresses #42 by cleaning up the vignette image paths.

My proposed structure is:

• A figures/ directory under the vignettes/ directory.
• Each vignette/article that uses figures has a subdirectory under figures/ with a name matching the name of the article (i.e. for an article titled my_article.Rmd, any images should be stored in the figures/my_article directory.

I cleaned up the 3 existing articles which use images to follow the above structure, and verified that the articles still build correctly locally (if someone could verify independently that would be great!)

[ChristopherMancuso]

@Andrew0Hill when you say build correctly locally do you mean something different than knitting the rmd file? Or you talking about packagedown? I've never used package down is this what I would do?

install.packages("pkgdown")
Run once to configure your package to use and deploy pkgdown
usethis::use_pkgdown_github_pages()
Preview your site locally before publishing
pkgdown::build_site()

and do this from the main directory of the branch?

[Andrew0Hill]

I've just been doing:

install.packages("pkgdown")
pkgdown::build_site()

That will try to generate the HTML pages for everything and then launch the (local) site in your browser.

[ChristopherMancuso]

I checked this out I was able to see that all the images and the vignettes were built correctly. I think I have some things to learn about build_site() as I had to run that command a number of times and then manually install a number of packages I didn't have when it would fail to run. I got it to woke in the end though.

[petersonR]

Thanks! Closing/merging now.