Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/log/log_test.go

@@ -0,0 +1,101 @@
+package log
+
+import (
+	"bytes"
+	"log"
+	"strings"
+	"testing"
+
+	"github.com/coredns/coredns/plugin/pkg/dnsrecorder"
+	"github.com/coredns/coredns/plugin/pkg/response"
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+func TestLoggedStatus(t *testing.T) {
+	var f bytes.Buffer
+	rule := Rule{
+		NameScope: ".",
+		Format:    DefaultLogFormat,
+		Log:       log.New(&f, "", 0),
+	}
+
+	logger := Logger{
+		Rules: []Rule{rule},
+		Next:  test.ErrorHandler(),
+	}
+
+	ctx := context.TODO()
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnsrecorder.New(&test.ResponseWriter{})
+
+	rcode, _ := logger.ServeDNS(ctx, rec, r)
+	if rcode != 0 {
+		t.Errorf("Expected rcode to be 0 - was: %d", rcode)
+	}
+
+	logged := f.String()
+	if !strings.Contains(logged, "A IN example.org. udp 29 false 512") {
+		t.Errorf("Expected it to be logged. Logged string: %s", logged)
+	}
+}
+
+func TestLoggedClassDenial(t *testing.T) {
+	var f bytes.Buffer
+	rule := Rule{
+		NameScope: ".",
+		Format:    DefaultLogFormat,
+		Log:       log.New(&f, "", 0),
+		Class:     response.Denial,
+	}
+
+	logger := Logger{
+		Rules: []Rule{rule},
+		Next:  test.ErrorHandler(),
+	}
+
+	ctx := context.TODO()
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnsrecorder.New(&test.ResponseWriter{})
+
+	logger.ServeDNS(ctx, rec, r)
+
+	logged := f.String()
+	if len(logged) != 0 {
+		t.Errorf("Expected it not to be logged, but got string: %s", logged)
+	}
+}
+
+func TestLoggedClassError(t *testing.T) {
+	var f bytes.Buffer
+	rule := Rule{
+		NameScope: ".",
+		Format:    DefaultLogFormat,
+		Log:       log.New(&f, "", 0),
+		Class:     response.Error,
+	}
+
+	logger := Logger{
+		Rules: []Rule{rule},
+		Next:  test.ErrorHandler(),
+	}
+
+	ctx := context.TODO()
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnsrecorder.New(&test.ResponseWriter{})
+
+	logger.ServeDNS(ctx, rec, r)
+
+	logged := f.String()
+	if !strings.Contains(logged, "SERVFAIL") {
+		t.Errorf("Expected it to be logged. Logged string: %s", logged)
+	}
+}