Updates the requirements on [num-bigint](https://github.com/rust-num/num-bigint) to permit the latest version.
- [Release notes](https://github.com/rust-num/num-bigint/releases)
- [Changelog](https://github.com/rust-num/num-bigint/blob/master/RELEASES.md)
- [Commits](https://github.com/rust-num/num-bigint/compare/num-bigint-0.3.0...num-bigint-0.4.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

* add folder structures similar to `ark-poly`

* add evaluate impl for DensePolynomialVar

* add tests

* fix no-std

* use ark_std::rand instead of SeedableRng

* add changelog

Co-authored-by: Weikeng Chen <w.k@berkeley.edu>

Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

Co-authored-by: Nicholas Ward <npward@berkeley.edu>

* Implement CanonicalSerialize/Deserialize improvements

* Improve code readability by using cursor

* Add tests for uncompressed serialization

* Improve serialization size (do not require full u64 limbs to be serialised)

* Change Flags to enum types

* Split up serialization with and without flags.

* Implement simple derive macro

* Derive traits for Groth16 and GM17 keys and proofs

* Update API of EvaluationDomain

* Update gm17 to use new API

* Move fft infrastructure to its own crate

* Fix gm17 to work with ff-fft

* Refactor polynomial infrastructure

* Change .travis-yml to not compile in release and to not run DPC tests

own crate.