0.4

• 73:
  Support assignment of enum values in FBS
• 72:
  Fix const-access for ZeroBuf vector on ConstAllocator parent, needed after #71
• 71:
  Fix update of ZeroBuf objects stored in a ZeroBuf vector after toJSON()
• 69:
  Allow empty ZeroBufs with empty JSON payload from HTTP server PUT requests
• 68:
  Support partial JSON updates
• 67:
  • Fix compilation error when having multiple FBS enums in one namespace
  • Maintain order of FBS fields in JSON schema
• 65:
  • JSON schema generated from FBS, available in ZeroBuf::getSchema() and
    ZeroBuf::ZEROBUF_SCHEMA
  • enum class for enums instead of 'old' enums; breaks existing enum names
  • fix wrong JSON value for empty arrays (was 'null', is '[]' now)