Replace Cacoo implementation with https://gist.github.com/pepijnve/2d4059db5d827462b5cd
Thanks to Pepijn Van Eeckhoudt!
Adjust code by reference to https://github.com/pepijnve/asciidoctor-diagram/tree/afbc882cef8fbdc06f2504196c5fbac903800a37
Fix an require error
Update Source parent class (which must be a class, not a module)
Get this extension working
Update README, add credits to Pepijn Van Eeckhoudt
Fix link markdown
Change the superclass of Source to API::BasicSource
Update README to use block macro syntax and set the alt text of the image tag.
Remove uneeded file
Follow changes asciidoctor-diagram/api/diagram to asciidoctor-diagram/extensions
Merge pull request #1 from hnakamur/enhance_by_pepijnve

Make implementation up to date to asciidoctor-diagram