Add tip to adjust README

Telling people to add description and link to repository.

1. Checking that `index.md` has `root` set to '.'
2. Checking that `_config.yml` has `root` set to '..'

AMY's form for self-organized workshops

Close #330.

Closes #336.

Fix "br" typo causing ugly rendering (epub only)

</br> instead of <br/> renders fine in the browser but not in an epub

fix swc_github_io versus swc_github

index.html uses `swc_github_io`, _config.yml uses `swc_github`. This is I think what caused links in the final workshop website to be wrong.

Updated Git install instructions

changed link to windows installer under SQLite

An internally-defined Markdown link has the form [xxx][yyy].  If the
ID 'yyy' doesn't resolve, the text is left as-is, so we check for
that, then subtract those that reference configuration values using
'{{'.  It's a hack, but it'll catch at least a few things.