chore: bump version number

feat: add `to_path_buf` method to `MailEntry`

perf: improve performance slightly

docs: update README

build: bump version

feat!: `list_new` now moves messages into `cur`

A new method `peek_new` has also been added, which does not move entries

docs: add features part of README

fix: remove size info on mail entries

Quotas are not supported yet.

build: update Cargo.toml

docs: update README

test: fix tests

more features

rewritten maildirpp crate

tests do not pass yet, and some functionality of maildir++ is still
missing