use the passed in option to determine what xsl to run
XSL arg is optional
start.html now included in zipped EPUB
Module TOC links to correct HTML file

Instead of linking to `content/content/pr01.html` it links to
`content/pr01.html`
Explicitly include the start.html file when creating an epub/zip file

It appears `zip` on different OSs handle a string with a wildcard
differently (OSX will match all the files and include them and debian
will seaerch for and add a single file named "*.html"
Merge pull request #41 from Connexions/start-xsl

Offline zip now has start.html