Documentation: adding context

[DanielHeath]

The documentation at https://docs.honeycomb.io/getting-data-in/ruby/beeline/#adding-context-to-events shows how to add context to a sinatra app.

To add it to a rails app, you need to change:

• request.env instead of env
• Rack::Honeycomb.add_field to a method that exists (this missing method is also referenced in the upgrade guide). Actually, if someone could let me know what that method is, that'd be super handy.

[martin308]

@DanielHeath this is now much easier in v1.0.0!

Honeycomb.start_span(name: "slow_operation") do |span|
  span.add_field("interesting_thing", "banana")
end