update README

some test coverage for Value::iterator (open-source-parsers#1093)

\open-source-parsers#979 Fix parseFromStream definition

This patch fixes issue open-source-parsers#979, where the parseFromStream definition in
the header is different from the implementation.

Medium size release containing bug fixes, enhancements

BORLAND compatible

1.8.4; soversion=20

Merge pull request open-source-parsers#655 from cdunn2001/fix-649

Fixes open-source-parsers#649
Fixes open-source-parsers#654

Merge pull request open-source-parsers#652 from cdunn2001/meson-not-s…

…cons

Meson not scons; 1.8.2<-1.8.1

Require cmake>=3.1

Plus some other build-related changes. I don't think there is anything
functionally different from 1.7.7, or even any binary incompatibilities, but
the cmake change is significant.