Periodic boundary conditions: updated

[sdd]

• feat: PBC now expects the period as an argument when querying using PBC functions, rather than storing it in the tree. This prevents the memory layout of the KdTree struct from changing with the introduction of PBC, which would force existing users to have to rebuild any serialized trees if they wanted to upgrade.
• tests: PBC tests refactored to move common brute force PBC check code and data/query/tree generating into separate private function
• tests: PBC tests use neater float asserts from approx package
• tests: Rayon removed and PBC unit test query point and data point count reduced to improve unit test run time
• style: re-ran cargo fmt and cargo clippy and fixed clippy lints that were introduced

[sdd]

Addresses https://github.com/sdd/kiddo/issues/19

[cavemanloverboy]

Forgot to comment here saying it all looks good to me