Install one package from a newer Debian release

For example one package from Debian Stretch on Jessie:

1. Add into /etc/apt/apt.conf:

APT::Default-Release "jessie";

2. Add into /etc/apt/sources.list:

deb http://http.debian.net/debian/ stretch main
deb http://security.debian.org/ stretch/updates main

3. Run apt-get update

4. Run aptitude install -t stretch packagename