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/pprof/setup_test.go

@@ -0,0 +1,34 @@
+package pprof
+
+import (
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestPProf(t *testing.T) {
+	tests := []struct {
+		input     string
+		shouldErr bool
+	}{
+		{`pprof`, false},
+		{`pprof 1.2.3.4:1234`, false},
+		{`pprof :1234`, 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)
+		}
+	}
+}