Make CoreDNS a server type plugin for Caddy (#220)

* Make CoreDNS a server type plugin for Caddy

Remove code we don't need and port all middleware over. Fix all tests
and rework the documentation.

Also make `go generate` build a caddy binary which we then copy into
our directory. This means `go build`-builds remain working as-is.

And new etc instances in each etcd test for better isolation.
Fix more tests and rework test.Server with the newer support Caddy offers.

Fix Makefile to support new mode of operation.

middleware/pprof/pprof.go

@@ -12,7 +12,7 @@ type Handler struct {
 	mux *http.ServeMux
 }
 
-func (h *Handler) Start() error {
+func (h *Handler) Startup() error {
 	if ln, err := net.Listen("tcp", addr); err != nil {
 		log.Printf("[ERROR] Failed to start pprof handler: %s", err)
 		return err

middleware/pprof/setup.go

@@ -0,0 +1,40 @@
+package pprof
+
+import (
+	"sync"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("pprof", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	found := false
+	for c.Next() {
+		if found {
+			return c.Err("pprof can only be specified once")
+		}
+		if len(c.RemainingArgs()) != 0 {
+			return c.ArgErr()
+		}
+		if c.NextBlock() {
+			return c.ArgErr()
+		}
+		found = true
+	}
+
+	handler := &Handler{}
+	pprofOnce.Do(func() {
+		c.OnStartup(handler.Startup)
+		c.OnShutdown(handler.Shutdown)
+	})
+
+	return nil
+}
+
+var pprofOnce sync.Once

middleware/pprof/setup_test.go

@@ -0,0 +1,32 @@
+package pprof
+
+import (
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestPProf(t *testing.T) {
+	tests := []struct {
+		input     string
+		shouldErr bool
+	}{
+		{`pprof`, false},
+		{`pprof {}`, true},
+		{`pprof /foo`, true},
+		{`pprof {
+            a b
+        }`, true},
+		{`pprof
+          pprof`, true},
+	}
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		err := setup(c)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %v: Expected error but found nil", i)
+		} else if !test.shouldErr && err != nil {
+			t.Errorf("Test %v: Expected no error but found error: %v", i, err)
+		}
+	}
+}