fix go vet errors

Author: Stebalien

json_test.go

@@ -36,7 +36,7 @@ func TestMarshal(t *testing.T) {
 		}
 
 		if len(m) != 3 {
-			t.Errorf("expected three map elements, got ", len(m))
+			t.Errorf("expected three map elements, got %d", len(m))
 		}
 
 		if m["Message"].(string) != tc.msg {

option.go

@@ -106,7 +106,7 @@ var converters = map[reflect.Kind]converter{
 func (o *option) Parse(v string) (interface{}, error) {
 	conv, ok := converters[o.Type()]
 	if !ok {
-		return nil, fmt.Errorf("option %q takes %s arguments, but was passed %q", o, o.Type, v)
+		return nil, fmt.Errorf("option %q takes %s arguments, but was passed %q", o.Name(), o.Type(), v)
 	}
 
 	return conv(v)

option_test.go

@@ -88,11 +88,11 @@ func TestParse(t *testing.T) {
 		if err != nil && err.Error() != tc.err {
 			t.Errorf("unexpected error: %s", err)
 		} else if err == nil && tc.err != "" {
-			t.Errorf("expected error %q but got nil")
+			t.Errorf("expected error %q but got nil", tc.err)
 		}
 
 		if v != tc.v {
-			t.Error("expected %v but got %v", tc.v, v)
+			t.Errorf("expected %v but got %v", tc.v, v)
 		}
 	}
 }