Merge pull request #17 from bodiam/master

Some improvements
Make asciidoctor resolve relative includes. Make preview resolve relative images. Enable preview-as-you-type. Don't jump at end of preview.
Merge pull request #23 from ahus1/ahus1_previewasyoutype

Add preview as you type for split view
Merge remote-tracking branch 'upstream/master'
GITHUB-18 Changed link to https://github.com/asciidoctor/idea-asciidoc, because it should point to the plugin homepage.