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/chaos/setup_test.go

@@ -0,0 +1,54 @@
+package chaos
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mholt/caddy"
+)
+
+func TestSetupChaos(t *testing.T) {
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedVersion    string // expected version.
+		expectedAuthor     string // expected author (string, although we get a map).
+		expectedErrContent string // substring from the expected error. Empty for positive cases.
+	}{
+		// positive
+		{
+			`chaos v2`, false, "v2", "", "",
+		},
+		{
+			`chaos v3 "Miek Gieben"`, false, "v3", "Miek Gieben", "",
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		version, authors, err := chaosParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+
+		if !test.shouldErr && version != test.expectedVersion {
+			t.Errorf("Chaos not correctly set for input %s. Expected: %s, actual: %s", test.input, test.expectedVersion, version)
+		}
+		if !test.shouldErr && authors != nil {
+			if _, ok := authors[test.expectedAuthor]; !ok {
+				t.Errorf("Chaos not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, test.expectedAuthor, "Miek Gieben")
+			}
+		}
+	}
+}