v0.6.13

• Use the maybe-unit crate in place of soon-to-be-deprecated std::mem::uninitialized (#180). When built with Rust 1.36 or later, this fixes a source of undefined behavior. It also fixes deprecation warnings in Rust 1.39 and later, and test failures when run in MIRI. In Rust 1.35 and earlier it provides some safety improvements but does not completely eliminate undefined behavior. (However, we are not aware of any cases where the undefined behavior causes bugs in practice in those toolchains.)