Move wiki to GitHub Pages

[ejball]

We could presumably use Jekyll to generate the table of contents to avoid title duplication. Perhaps we could generate "see also" link titles as well.

[amanda-mitchell]

@bgrainger and I discussed this and opted for the wiki because we want to encourage casual edits from consumers of the package.

However, it might be interesting/worthwhile to add a build step that validates/updates the wiki based on the code.