version 18

• Change NeoJSONWriter to give an error when map keys/names are not strings (as per the standard)
• Switch CI from Travis to GitHub Actions
• Add NeoJSONWriter>#floatPrinter: to set an optional float printer
• Make NeoJSONFloatPrinter more configurable
• Make NeoJSONObject inherit from OrderedDictionary (as a convenience)
• Patch a bug in OrderedDictionary>>#at:ifPresent:ifAbsentPut:
• Use OSPlatform current lineEnding as default for NeoJSONWriter's newLine setting
• Add support for different species of String in NeoJSONReader streams
• Add NeoJSONObject>>#at:at:[put:] overrides delegated to #atPath:put:
• Improve Float parsing accuracy following improvements made in STON