updates syntax in preparation for 1.5 release

- vbar and brvbar mapping
- paragraph hardbreaks
Merge pull request #225 from graphitefriction/1-5-docs

updates syntax in preparation for 1.5 release
updates sections and subs for 1.5 release

- sectnumlevels attribute added
- specialchars alias
- substitution alias for the inline pass macro
- appending and removing subs to the defualt subs list
- pass style and subs groups table
Merge pull request #226 from graphitefriction/1-5-docs

updates sections and subs for 1.5 release
udates include dir and video for 1.5

- include directive can handle spaces
- video playback start and end range attritbutes
- documents  asciidoctor/asciidoctor#695 and asciidoctor/asciidoctor#886
Merge pull request #227 from graphitefriction/1-5-docs

udates include dir and video for 1.5
adds stem section to user manual

- stem attribute, inline macro, stem block
- latexmath and asciimath interpreters
- documents asciidoctor/asciidoctor#492, asciidoctor/asciidoctor#760,
  asciidoctor/asciidoctor#1005
Merge pull request #228 from graphitefriction/1-5-docs

adds stem section to user manual
Fix result of "Inline anchors" in asciidoc-syntax-quick-reference
Merge pull request #230 from ge0ffrey/patch-1

Fix result of "Inline anchors" in asciidoc-syntax-quick-reference
resolves #229 fix XML-friendly callout example
Merge pull request #231 from mojavelinux/issue-229

resolves #229 fix XML-friendly callout example
updates syntax highlighting examples

- adds pygments attributes and example snippet
- adds coderay section
- adds coderay attributes
- adds pygments output image
- closes #162
- closes asciidoctor/asciidoctor#637
- documents asciidoctor/asciidoctor#604
Merge pull request #232 from graphitefriction/1-5-docs

updates syntax highlighting examples
minor copy fixes
Revert "Fix result of "Inline anchors" in asciidoc-syntax-quick-reference"
Merge pull request #233 from asciidoctor/revert-230-patch-1

Revert "Fix result of "Inline anchors" in asciidoc-syntax-quick-referenc...
clarify passthrough usage warning
fix tip about escaping attribute list that precedes formatted text
document how to escape unconstrained formatting marks