added a pretty output to JString. Initial.

testing/jstring_test.cpp

@@ -27,6 +27,7 @@ int main(int argc, char **argv) {
    test1["object1"] = "{\"attr1\":\"value1\",\"attr2\":\"value2\",\"attr3\":\"value3\"}";
    test1["object1.attr2"] = "{\"xattr1\":\"xvalue1\",\"xattr2\":\"xvalue2\",\"xattr3\":\"xvalue3\"}";
    test1["object1.attr3"] = "Im not an object";
+//   test1["age"] = 64; future
 
    std::cout << test1 << std::endl;
 
@@ -58,6 +59,8 @@ int main(int argc, char **argv) {
    test9 = test1["object1"];
    std::cout << test9 << std::endl;
    std::cout << test9["attr3"] << std::endl;
+
+   std::cout << test1.pretty() << std::endl;
    
    return 0;
 }