Tweaked the pow function in bignums/mpz
o If the exponent is a float, the result will now be a float
(ie, 1000000000000**0.5 is now 1000000.0, not 1)
o Added ``**
o Removed arbitrary size limit entirely.
It's up to the programmer to avoid 999 ** 9999999999999999999999.
You still get an error if the result is too large for your memory.