Add FasterPath.add_trailing_separator

[mble]

• Implement Pathname.add_trailing_separator in Rust
• Hook Rust function into FasterPath as FasterPath.add_trailing_separator
• Add FasterPath.add_trailing_separator monkeypatch and refinement
• Add tests and benchmarks for FasterPath.add_trailing_separator against Pathname.add_trailing_separator

https://github.com/danielpclark/faster_path/issues/43

[danielpclark]

Looks good. Can you add a few tests that compare the two methods against each other? assert_eq FasterPath.add_trailing_sparator(str), Pathname.allocate.send(:add_trailing_separator, str) and in the stats section of the readme since Pathname's method is an instance method it would be represented with a pound symbol Pathname#add_trailing_separator . That's my fault for labelling it wrong in this open issue.

[mble]

All done @danielpclark