for GNOME 3.10 / 3.12 / 3.14 / 3.16 / 3.18 / 3.20
To use the extension, run:
git clone http://github.com/saligrama/gnome-shell-extension-suspend-button
zip -r gnome-shell-extension-suspend-button.zip gnome-shell-extension-suspend-button
Then, go to GNOME tweak tool and install the extension and enable it.