Incorrect resource is set when wrapping multiple methods in a single call

[joshuay03]

The issue stems from the resource being set for the first method if the passed in value is falsey, and then the value being used in subsequent methods due to the memoisation:

ddtrace-rb-method-wrapper/lib/datadog_trace_wrapper.rb

Line 28 in 2ee71cd

resource ||= "#{self.class.name}##{m}"

I've got a branch with a reproducing spec: master...joshuay03:ddtrace-rb-method-wrapper:multi-wrapped-resources

Failure

Failures:

  1) DdtraceWrapper wrap multiple :methods wraps with all the available args applicable to each method
     Failure/Error: expect(Datadog::Tracing).to receive(:trace).with('multi_span', service: ENV['DD_TRACE_METHOD_WRAPPER_SERVICE'], resource: 'DatadogTraceWrapperSpec#multi_wrapped_value_1')

       (Datadog::Tracing).trace("multi_span", {:resource=>"DatadogTraceWrapperSpec#multi_wrapped_value_1", :service=>"rspec"})
           expected: 1 time with arguments: ("multi_span", {:resource=>"DatadogTraceWrapperSpec#multi_wrapped_value_1", :service=>"rspec"})
           received: 2 times with arguments: ("multi_span", {:resource=>"DatadogTraceWrapperSpec#multi_wrapped_value_1", :service=>"rspec"})
     # ./spec/datadog_trace_wrapper_spec.rb:65:in `block (3 levels) in <top (required)>'

Finished in 0.01564 seconds (files took 0.33626 seconds to load)
5 examples, 1 failure

Failed examples:

rspec ./spec/datadog_trace_wrapper_spec.rb:64 # DdtraceWrapper wrap multiple :methods wraps with all the available args applicable to each method

Note that I had to update some of the API usage to get the specs to run with the latest 1.x version of ddtrace.

While I'm here, are there any plans to support ddtrace v2 (renamed to datadog)?