v1.2.0

• Remove default export (use import { Arena } from "..." instead)
• Rename send (one of exported functions) to json
• Support "json" as values that can be set with isMarshalable (JSON marshaling mode)
• Change default isMarshalable value (marshaling mode) to JSON mode
• evalCode now returns unwrapped objects
• Add support for exposing functions that return objects (#2)
• Fix possible minor errors
• Update dependencies