Changes since 6.0.0

• Add namespacing support #290 @stephenberry
• Add utf parsing support
• cheatsheet.md updates
• add_class utility support for scoped enums #306 @StanEpp
• Parser optimizations #300 @niXman
• Various JSON fixes #377 #400 #409 #371 @totalgee @dinghram @arcoRocks
• Various cleanups, bugfixes and warning fixes and minor performance improvements
• Support for C++17 compilers!
• Support for UTF8 BOM #439 @AlekMosingiewicz @MarioLiebisch