Added two new output formats

• svg_object: generate a object tag for embedding svg diagrams
• svg_inline: insert svg diagram directly in the document

Fixed wrong HTML attribute `classes`

The generated HTML was containing a wrong classes attribute instead of
the class attribute.

GitLab/GitHub support and variuos fixes

• added support for GitLab/GitHub syntax
• added a title macro option, for generating diagram tooltips
• fixed generation of class and alt attributes
• fixed handling of unicode characters

Inline images

• images are now inlined, no more files around
• added txt diagram format

Big thanks to @kubilus1.