* bin(num) can convert ZERO and negative decimal numbers to binary. Consistent with built-in python bin(x) function.
* bin(num) can convert ZERO and negative decimal numbers to binary. Consistent with built-in python bin(x) function.
* Added doctests. bin(num) can convert ZERO and negative decimal numbers to binary. Consistent with built-in python bin(x) function.
* Added doctests. bin(num) can convert ZERO and negative decimal numbers to binary. Consistent with built-in python bin(x) function.
* Added doctests. bin(num) can convert ZERO and negative decimal numbers to binary. Consistent with built-in python bin(x) function.
* doctests still failing.
* Doctests added.