Add to_base() and from_base() to Math::BigInt and corresponding library
methods _to_base() and _from_base() to Math::BigInt::Lib. This was inspired
by CPAN RT #122681.Fix Makefile.PL to reflect that Test::More is only needed for testing, not
for building.In the documentation for each of the to(bin|hex|oct|bytes) methods, add a
reference to the corresponding from(bin|hex|oct|bytes) method.