fix(http) avoid recursive sublanguage and tighten rules

[joshgoebel]

Currently it's too easy to trigger recursive sublanguages with
a file that contains multiple paragraph breaks (\n\n). http
can potentially fire over and over resulting in auto-detect on
the remaining content with all grammars over and over.

This tightens up the HTTP rules a lot to avoid this recursion
as well as reduce a lot of false positives.

Checklist

• Added markup tests, or they don't apply here because...
• Updated the changelog at CHANGES.md
• Added myself to AUTHORS.txt, under Contributors

[allejo]

<span class="hljs-attribute">Host</span><span class="hljs-punctuation">: </span>example.org

It feels kinda weird to me that the space is considered part of the "punctuation."

but this looks good 👍

[joshgoebel]

It feels kinda weird to me that the space is considered part of the "punctuation."

I no longer spend extra effort on inline spacing issues IF they would be difficult to solve.