Update to add build contraints to not compile in yaml support

in the case the golang version is less than golang 1.2

altsrc/helpers_test.go

@@ -0,0 +1,18 @@
+package altsrc
+
+import (
+	"reflect"
+	"testing"
+)
+
+func expect(t *testing.T, a interface{}, b interface{}) {
+	if !reflect.DeepEqual(b, a) {
+		t.Errorf("Expected %#v (type %v) - Got %#v (type %v)", b, reflect.TypeOf(b), a, reflect.TypeOf(a))
+	}
+}
+
+func refute(t *testing.T, a interface{}, b interface{}) {
+	if a == b {
+		t.Errorf("Did not expect %v (type %v) - Got %v (type %v)", b, reflect.TypeOf(b), a, reflect.TypeOf(a))
+	}
+}