04: Change to size type

[janniks]

Not 100% sure about this

In 04_02_template_parameter_categories.cpp#L11 maybe change:

- template<int I, int N>
+ template<int I, size_t N>

I believe, the current code should only work on systems that happen to alias size_t to int (rather than unsigned long for example) but I'm not really sure...

Change proposal