v1.0.0-rc.1

• url encode baggage keys and values
• add opentelemetry.io docs
• permit keyword list start_opts in Tracer macros.
• fix bug preventing configuring span processors
• fix tracer configuration merging
• split metrics out to experimental applications
• add service.name fallback and process resource attributes
• OTLP Exporter features and fixes:
  • upgrade grpcbox and log errors returned during export
  • add load of exporter app in configuration and comment on why
  • support path on traces endpoints
  • support OS environment variables for setting tracer to OTLP
  • exporter: support for endpoint and header configuration -- used for sending permission tokens to services like Honeycomb and Lightstep
  • endpoint parsing exporter fixes and small cleanup in tracer