Added more tests

re_test.go

@@ -40,6 +40,7 @@ var reTests = []struct {
 	{"a?b?c?", "ac", []matchIndex{{0, 2}}},
 	{"a?b?c", "abc", []matchIndex{{0, 3}}},
 	{"a?b?c", "acb", []matchIndex{{0, 2}}},
+	{"a(b|b)", "ab", []matchIndex{{0, 2}}},
 }
 
 func TestFindAllMatches(t *testing.T) {