simplify syntax for emitting layout message for the image block
escape double underscore in style name for bold text
Merge pull request #16 from mojavelinux/inline-quoted-fix

escape double underscore in style name for bold text
Break up code/command blocks by line, and the apply different styling on last line

Resolves #6
Merge branch 'image-block-fix' of github.com:mojavelinux/asciidoc-packt into mojavelinux-image-block-fix
Merge fix to image
Update keyword styling