Use relative URLs if baseUrl is not set or is "." (#117)

[moqmar]

No description provided.

[mnapoli]

Could you explain please?

[moqmar]

This solves issue #117 - if the baseUrl is empty unset (an empty string still means "the root of the current domain") or ".", it is dynamically set for every page - pages in the main directory get a baseUrl of ., in a first-level subdirectory .., second-level gets ../.., and so on. That way, the generated HTML files can be hosted everywhere and even work when opened from the local file system.