Add support for different integer widths using -w flag,
i.e. moo -w 32 to use 32 bit integers.  It would be nice to support
multiple -w flags as well.

Add support for casting, i.e. -c32 would show what happens when you
cast to int32_t.  Not sure how to handle casting signed vs unsigned.

Add regression tests for single number input, all base output.