Avoid HTML comment preamble in man page output from Pandoc

[olleolleolle]

Description:

This PR changes the way man pages are generated, avoiding a preamble that mentions Pandoc. Fixes #398

That preamble is fine to have in HTML, not in man pages.

In addition, regenerate docs.

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I will abide by the code of conduct.

[olleolleolle]

Aha, tests fail in an interesting way:

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	%2FUsers%2Folle.jonsson%2Fopensource%2Fgemstash%2Ftmp%2Ftest_base%2Fgemstash.db

Somehow the path to the sqlite DB file is created URL-encoded.

Removing the CGI.escape around the db_path makes the test pass. See 14126ca