Socket is used but there's no "require"

[sullerandras]

I ran into this issue with Ruby 2.3.3:

NameError: uninitialized constant Trace::Endpoint::Socket
# .../gems/zipkin-tracer-0.21.0/lib/zipkin-tracer/trace.rb:137:in `local_endpoint'
# .../gems/zipkin-tracer-0.21.0/lib/zipkin-tracer/tracer_factory.rb:25:in `tracer'
# .../gems/zipkin-tracer-0.21.0/lib/zipkin-tracer/rack/zipkin-tracer.rb:14:in `initialize'

It seems like Socket is used in Zipkin, but it is not required explicitly with require 'socket'.