Optimize Writer::WriteString() with SIMD

Add stream position check to reader unit tests

Add Value::Get/SetFloat(), Value::IsLossLessFloat/Double()

Fix #341

Support {0, } and {0, m} in Regex

Add encoding validation option for Writer/PrettyWriter

Fix #509 by checking Nan/Inf when writing a double

Add optional unresolvedTokenIndex parameter to Pointer::Get()

Add Jsonx example for converting JSON into JSONx (a XML format)

Add iostream wrapper