Golang opentelemetry-go draft API (incomplete) (#9)

* Work in progress from https://github.com/lightstep/opentelemetry-golang-prototype

* Renames

* Rename

* Finish rename

* Rename packages

* README

example/http/server/server.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"io"
+	"net/http"
+
+	"github.com/open-telemetry/opentelemetry-go/api/core"
+	"github.com/open-telemetry/opentelemetry-go/api/log"
+	"github.com/open-telemetry/opentelemetry-go/api/tag"
+	"github.com/open-telemetry/opentelemetry-go/api/trace"
+	"github.com/open-telemetry/opentelemetry-go/plugin/httptrace"
+
+	_ "github.com/open-telemetry/opentelemetry-go/exporter/loader"
+)
+
+var (
+	tracer = trace.GlobalTracer().
+		WithService("server").
+		WithComponent("main").
+		WithResources(
+			tag.New("whatevs").String("nooooo"),
+		)
+)
+
+func main() {
+	helloHandler := func(w http.ResponseWriter, req *http.Request) {
+		attrs, tags, spanCtx := httptrace.Extract(req)
+
+		req = req.WithContext(tag.WithMap(req.Context(), tag.NewMap(core.KeyValue{}, tags, core.Mutator{}, nil)))
+
+		ctx, span := tracer.Start(
+			req.Context(),
+			"hello",
+			trace.WithAttributes(attrs...),
+			trace.ChildOf(spanCtx),
+		)
+		defer span.Finish()
+
+		log.Log(ctx, "handling this...")
+
+		io.WriteString(w, "Hello, world!\n")
+	}
+
+	http.HandleFunc("/hello", helloHandler)
+	err := http.ListenAndServe(":7777", nil)
+	if err != nil {
+		panic(err)
+	}
+}