default renamed to substitution and covered with tests

examples/basic_usage.cpp

@@ -23,7 +23,7 @@ SERIALIZE(MyStruct) {
     return s.
             value(o.i).
             value(o.e).
-            container(o.fs);
+            container(o.fs, 100);
 }
 
 void print(const char* msg, const MyStruct& v) {
@@ -36,6 +36,8 @@ void print(const char* msg, const MyStruct& v) {
     std::cout << std::endl << std::endl;
 }
 
+using namespace bitsery;
+
 int main() {
     //set some random data
     MyStruct data{};