Improve documentation

[vinipsmaker]

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[vinipsmaker]

Hints from @breese (copy-pasted-edited without authorization from a private email, but doesn't look to reveal any sensitive information, so I'm exposing it anyway):

then I suggest that you introduce the main
players elsewhere (e.g. on the main page, or at the beginning of the
tutorial.)

main players: http::socket, http::message, and some of the algorithms

Email received about at the time that I have removed the introduction page.