v0.4.0

This release removes the claim of compatability with Rust 1.24, as a patch update to notify changes the minimum requirement to 1.26.

hotwatch 0.3 can still be used with Rust 1.24 if you pin the notify dependency to 4.0.6.

• Only the latest stable release of Rust is guaranteed to be compatible.
• hotwatch::Error now implements std::error::Error.