new method to implement circular allocator
ascii drawing, change template parameter order

The first template parameter for allocator-related classes is now the
payload instead of the index type. Use std::numeric_limits<>::max() for
maximum pool size.
more info when bad reference exception
install target
missing file
better pointer semantic by using nullptr_t
fixed some bugs when using OPTIM_POS, new ring allocator

new ring allocator that allows to set the size of the ring buffer and
stores current index to non-volatile memory.