Add link to conversion script (Confluence XHTML to AsciiDoc)

[mojavelinux]

Add a link to the following script on the migrations page that converts Confluence XHTML to AsciiDoc:

https://gist.github.com/melix/6020336

[jaredmorgs]

Next action:

• create new section in https://github.com/asciidoctor/asciidoctor.org/blob/ed5e4f38159872c1dbfe2a42d8a0aef5a2d7cfb5/docs/user-manual.adoc#conversions-and-migrations.
• add link to page.
• describe what the script does in summary.

Should we also link to the Markdown to Asciidoctor script you created as well in this section @mojavelinux ?

Anything else that deserves mention here?

[mojavelinux]

Yes, add the link to https://github.com/opendevise/kramdown-asciidoc. And we might as well add a link to DocbookRx as well https://github.com/opendevise/docbookrx. We can mention that the plugin for IntelliJ IDEA has a built-in tool for converting from Markdown to AsciiDoc.

[jaredmorgs]

I'll reserve the kramdown-asciidoc fix for #462

I need to add the DocbookRx to this commit.

[jaredmorgs]

I will now add the DocBookRx content into the guide.

[mojavelinux]

Ye-ha!

[mojavelinux]

Merged as 5288b26 with additional revisions in 84ddece.