Update twang requirement from 0.3 to 0.4

[dependabot-preview[bot]]

Updates the requirements on twang to permit the latest version.

Changelog

Sourced from twang's changelog.

[0.4.0] - 2020-11-11

Added

• Add Room struct for creating various types of reverb and echoes.

Changed

• Mix trait can now be used with either borrowed or unborrowed data.
• All methods on Signal that took f64 now take Into<Self>
• Rename Sample.amp() to Sample.gain()

[0.3.0] - 2020-08-26

Changed

• Depend on fon for audio types.
• Use simple PRNG for white noise instead of rand crate.
• Replace Wave with Synth and Fc (frequency counter)
• Replace Sample with Signal (which is slightly different than fon's Mono64
• Replace SampleSlice trait with Mix trait

Removed

• prelude module

[0.2.0] - 2018-08-16

Changed

• Newtype'd everything.
• Uses operator overloading now.

[0.1.0] - 2018-08-13

Added

• Code

Commits

• 73f2ebb v0.4.0
• ac63f2e Merge branch 'working' into master
• 74fa72f Prepare to release v0.4.0
• 0466ae6 Add noise gates.
• a292e26 Add Room API.
• 501b31d Fix documentation on Mix
• 1022f09 Update CHANGELOG.
• d90d7ba Improve Mix trait implementation.
• 4381ea2 Format code.
• 4317d8a Make methods on Signal consistent.
• Additional commits viewable in compare view

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