Support lazy ordered-list numbering

This patch changes dist.ini to insist on Markdent v0.23 or higher, so that lazy ordered-list numbering is supported properly. See the included test files for examples of what it can do now. (Markdent v0.23 went live on CPAN on December 13, 2013.)

Lazy and "drunken" list numbers are both explicitly referred to by the core Markdown spec (http://daringfireball.net/projects/markdown/syntax#list).