v0.5.6

fixes a weird old oversight where back() required &mut self for no reason.

v0.5.5

0.5.5 release

• fmts/clippy's all the code
• fixes all the derelict CI (and adds miri CI for all the tests)
• adds Entry::or_default and Entry::and_modify
• adds LinkedHashMap::drain

this is still basically in maintenance mode but I used this in anger enough recently to want to clean it up.