v0.16.0

What's Changed

• Minor cleanup by @apasel422 in #245
• Clean up parser tests by @apasel422 in #246
• Bump MSRV and edition by @apasel422 in #247
• Rework visitor documentation and example to clarify duplicate key caveat by @apasel422 in #248
• Clean up visitor impls by @apasel422 in #249
• Update specification tests by @apasel422 in #250
• Allow KeyRef/StringRef/TokenRef to be created from &[u8] by @apasel422 in #251
• Fix invalid UTF-8 error byte index in parse_display_string by @apasel422 in #254
• Fix regular expressions in Key/KeyRef and Token/TokenRef doc comments by @apasel422 in #255
• Remove #[must_use] from ParameterSerializer by @apasel422 in #257
• Bump version to 0.16 by @valenting in #258

Full Changelog: v0.15.0...v0.16.0