Typos README

Hey, thanks for this great library which I've used in many occasions now. I know it's not much, but I wanted to contribute at least a tiny bit back to you by this PR :-) Keep up the good work!

adding std::ios_base::binary when opening all_unicode.json.cbor

add forwarding references to json_ref constructor

fixes #805

Add transparent comparator and perfect forwarding support to find() and count()

Already covered by AppVeyor

Instead implement @gregmarr's PR comments that perfect forwarding should be used. Also cleaned up cpp language standard detection.

Hopefully, #764 fixed this.

Simplified istream handing #367

Copied from solution to https://github.com/nlohmann/json/issues/464

This avoids unnecessary string copies on often used
find().

Error : 'identifier "size_t" is undefined' in linux

Fix Visual Studio 2017 warnings