DenseOrSparsePolynomial::divide_with_q_and_r never returns None

[swasilyev]

It panics at division by 0: https://github.com/arkworks-rs/algebra/blob/e554fa25a85e18b9bc0caeaf969483031daf7d5e/poly/src/polynomial/univariate/mod.rs#L109

Should we remove Option from the method signature?

[weikengchen]

The problem seems to be a decision between two choices:

• panic when the divisor is zero
• return none when the divisor is zero

which one is better? what do people think?

[weikengchen]

(ideally we will try not to panic)