changelog: 1.5.5
changelog: 1.5.5

This adds the notes after the release, which were overlooked.

rust-lang/regex,rust-lang/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang-nursery/regex,rust-lang/regex,rust-lang/regex,rust-lang/regex