Fix warnings: dereference of null pointer

Ignore GCC 8 warnings.

Misc. typos

Found via `codespell -q 3` in  downstream https://github.com/BlueBrain/Brayns

This reverts commit 0d2580f1.

Fix #1014

Add transcoding/validation to Writer::RawValue()

Fix #1152

Fix #1174

Fix #1170
Also fixed C++03 problem for using nullptr.

Fixed https://github.com/miloyip/rapidjson-gitbook/issues/1

Schema violation details

Suggestion for issue #1108

CMake cleanups

#1164

Fix reported violated schema pointer when that schema is remote

Bug when switching to std regex

Fix Travis build due to clang noexcept issue in unittest
Fix #1159

I could not switch to std regex after defining the two variables as in documents. Then I try to fix it in schema.h.

Add archiver example

Fix FileWriteStream doc

GetParseOffset

Fix uninitilized member Reader::state_

A simple (de)serialization framework using DOM and SAX API

Avoid inheritance from std::iterator

Instead of inheriting from the deprecated std::iterator
template, define the member typedefs needed for
std::iterator_traits directly.

Closes #1131.