Explore behavior of C++ parsers

[gnzlbg]

C++ is a widely used programming language in the server space (when validating JSON needs to happen fast). There are a lot of C++ json parsers:

• nlohmann/json: header only, easy to use, modern c++, not aiming at being the fastest (but still fast enough).
• RapidJSON: header-only, aiming at being the fastest c++ parser (can use SSE2 and SSE4.2, see configuration options), can trade conformance for speed (see options).
• folly/json: Facebook's json parser.
• JSON Spirit: implemented using Boost.Spirit.
• picojson: a lightweight JSON parser.
• V8 JavaScript Engine: has a C++ JSON parser.