build(deps): update num-bigint-dig requirement from 0.8.4 to 0.9.1

[dependabot]

Updates the requirements on num-bigint-dig to permit the latest version.

Changelog

Sourced from num-bigint-dig's changelog.

Release 0.2.2 (2018-12-14)

• The Roots implementations now use better initial guesses.
• Fixed to_signed_bytes_* for some positive numbers, where the most-significant byte is 0x80 and the rest are 0.

Contributors: @​cuviper, @​leodasvacas

Release 0.2.1 (2018-11-02)

• RandBigInt now uses Rng::fill_bytes to improve performance, instead of repeated gen::<u32> calls. The also affects the implementations of the other rand traits. This may potentially change the values produced by some seeded RNGs on previous versions, but the values were tested to be stable with ChaChaRng, IsaacRng, and XorShiftRng.
• BigInt and BigUint now implement num_integer::Roots.
• BigInt and BigUint now implement num_traits::Pow.
• BigInt and BigUint now implement operators with 128-bit integers.

Contributors: @​cuviper, @​dignifiedquire, @​mancabizjak, @​Robbepop, @​TheIronBorn, @​thomwiggers

Release 0.2.0 (2018-05-25)

Enhancements

• [BigInt and BigUint now implement Product and Sum][22] for iterators of any item that we can Mul and Add, respectively. For example, a factorial can now be simply: let f: BigUint = (1u32..1000).product();
• [BigInt now supports two's-complement logic operations][26], namely BitAnd, BitOr, BitXor, and Not. These act conceptually as if each number had an infinite prefix of 0 or 1 bits for positive or negative.
• [BigInt now supports assignment operators][41] like AddAssign.
• [BigInt and BigUint now support conversions with i128 and u128][44], if sufficient compiler support is detected.
• [BigInt and BigUint now implement rand's SampleUniform trait][48], and [a custom RandomBits distribution samples by bit size][49].
• The release also includes other miscellaneous improvements to performance.

Breaking Changes

• [num-bigint now requires rustc 1.15 or greater][23].

... (truncated)

Commits

• e53190d chore: Release num-bigint-dig version 0.9.1
• a6791cb fix: unused warning
• f186f87 chore: Release num-bigint-dig version 0.9.0
• 029dfe6 fix: update to MSRV 1.65 matching deps and some cleanups
• a341d12 feat!: update to rand 0.9
• 1382554 fix: handle future incompatibility warning
• a36dcaa feat: replace lazy_static with once_cell
• 53539b9 chore: Release num-bigint-dig version 0.8.5
• aa2a476 chore: fmt and test warning fix
• d94efb2 chore: Fix future incompatibility warning (#60)
• Additional commits viewable in compare view

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