Allow options for writing and parsing NaN/Infinity

This adds kWriteNanAndInfFlag to Writer to allow writing of nan,
inf and -inf doubles as "NaN", "Infinity" and "-Infinity",
respectively, and kParseNanAndInfFlag to Reader to allow parsing
of "NaN", "Inf", "Infinity", "-Inf" and "-Infinity". This is part
of issue #36, adding optional support for relaxed JSON syntax.

npm compliant package.json

fix some document problem

Added missing include guards in istreamwrapper.h and ostreamwrapper.h

Fix filterkeydom link

Define RAPIDJSON_HAS_CXX11_RVALUE_REFS directly in clang

This makes no difference except that it avoids "warning: macro expansion
producing 'defined' has undefined behavior" messages.

Add filterkey and filterkeydom examples

Also disable copy constructor/assignment operator

Adding spaces in Chinese doc

Try to fix cmake CMP0054 warning

Fix #606

Fix schema "required" keyword cannot handle duplicated keys

Fix #608

Fix regex crash

Due to dereferencing a pointer which may be invalidated

Improve coverage to 100%