Pathname#has_trailing_separator?

[mble]

I'd like to take on Pathname#has_trailing_separator?, as outlined in https://github.com/danielpclark/faster_path/issues/30

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• [x] Write Rust implementation of Pathname#has_trailing_separator? to FasterPath.has_trailing_separator?
• [x] Write refinements and monkey-patches for Pathname#has_trailing_separator? and map implementation to FasterPath.has_trailing_separator?
• [x] Write tests from existing sources proving FasterPath.has_trailing_separator? operates the same as Pathname#has_trailing_separator?
• [x] Write benchmarks in test/benches and compare the performance.
• [x] Also compare both the original to the new method to verify compatibility.

[danielpclark]

Thanks. I'll be getting to this soon! Not ignoring it! :+1: