* remove trailing / on meta tags
Meta tags are [void elements](https://html.spec.whatwg.org/multipage/syntax.html#void-elements) which means they are self closing, and do not require a closing tag, nor a trailing `/`.
The trailing `/` is something that was required in XHTML but [is ignored
in HTML](https://html.spec.whatwg.org/multipage/syntax.html#start-tags). Quoth the spec:
> On void elements, [the trailing slash] does not mark the start tag as self-closing but instead is unnecessary and has no effect of any kind. For such void elements, it should be used only with caution — especially since, if directly preceded by an unquoted attribute value, it becomes part of the attribute value rather than being discarded by the parser.
* remove trailing / on link tags
Probably still not perfect, but better.
- don't user avatar image. use banner for profile and post img, or
nothing
- most twitter metadata fields were redundant; twitter will parse out
opengraph ("og:"), so don't duplicate those
- add regular HTML description (for google, etc)
- include URI
- actually include text