Merge pull request #81 from oreillymedia/xmlschema

Added support for extra <div class="border-box"> in figure postprocessing
Added $custom.chunk.wrapper param that lets you specify a custom wrapper to put around chunk content.
Merge pull request #83 from oreillymedia/htmlbook-xsl

Added $custom.chunk.wrapper param that lets you specify a custom chunk wrapper
Allow <img/> elements to be included in aside.