Add release date to 0.7.1 in changelog
Add release date to 0.7.1 in changelog

bjodah/PyLaTeX,ovaskevich/PyLaTeX,sebastianhaas/PyLaTeX,JelteF/PyLaTeX,votti/PyLaTeX,votti/PyLaTeX,jendas1/PyLaTeX,ovaskevich/PyLaTeX,sebastianhaas/PyLaTeX,JelteF/PyLaTeX,jendas1/PyLaTeX,bjodah/PyLaTeX