Add indentation specs (wikitext, bf79f03)

Test user overrides of base indentation. The intention here is for incorporation in Haml templates (or any other templating system that takes care to produce beautifully-formatted HTML). The user can supply a base indentation level that matches the expected indentation level in the enclosing Haml template; in this way the wikitext-generated portion won't break the nice indentation of the template as a whole.

Signed-off-by: Greg Hurrell <greg@hurrell.net>