Fixes #72: support less restrictive equality comparison by the In rule

Author: qiangxue

in.go

@@ -4,10 +4,14 @@
 
 package validation
 
-import "errors"
+import (
+	"errors"
+	"reflect"
+)
 
 // In returns a validation rule that checks if a value can be found in the given list of values.
-// Note that the value being checked and the possible range of values must be of the same type.
+// reflect.DeepEqual() will be used to determine if two values are equal.
+// For more details please refer to https://golang.org/pkg/reflect/#DeepEqual
 // An empty value is considered valid. Use the Required rule to make sure a value is not empty.
 func In(values ...interface{}) InRule {
 	return InRule{
@@ -30,7 +34,7 @@ func (r InRule) Validate(value interface{}) error {
 	}
 
 	for _, e := range r.elements {
-		if e == value {
+		if reflect.DeepEqual(e, value) {
 			return nil
 		}
 	}

in_test.go

@@ -27,6 +27,7 @@ func TestIn(t *testing.T) {
 		{"t5", []interface{}{1, 2}, "1", "must be a valid value"},
 		{"t6", []interface{}{1, 2}, &v, ""},
 		{"t7", []interface{}{1, 2}, v2, ""},
+		{"t8", []interface{}{[]byte{1}, 1, 2}, []byte{1}, ""},
 	}
 
 	for _, test := range tests {