Made manpages explicit.

[pranomostro]

This commit removes the a2x dependency and the fulgurate-man script. It adds handwritten manpages.

Rationale: By removing the dependency, this commit increases stability and portability. It also makes fulgurate more streamlined with the rest of unix and the idea of unix in general.

[theq629]

I am trying to get back to maintaining this package. I'm going to aim to clean up the man pages, but I would still prefer to generate them from something so I don't have to duplicate the docs. Maybe argparse-manpage or click-man. I'll leave this open until I work that out though.