Bugfix release v0.3.1

• Nat::from_float() no longer produces leading zeroes and error when called with float in range 0..<1
• Changed return type of Nat::divmod() from tuple to pair
• Precompile arby's header when used in the test suite
• Misc. docs changes

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Here follows an auto-generated summary of the changes:

What's Changed

• feat divmod: change return type to std::pair by @deadb0d4 in #87
• Bugfix: leading zero error when creating Nat from float by @saxbophone in #92

New Contributors

• @deadb0d4 made their first contribution in #87

Full Changelog: v0.3.0...v0.3.1