gnome-ring - UI is extremely small on HiDPI displays / no HiDPI support

Issue generated from Tuleap's migration script. Originally submitted by: Nicholas Ermolov (nermolov)

* Environment:
Arch Linux
gnome-ring 1.0.0 - 1e2dd354
2560x1440 display on 13 in laptop
i3wm with Xft.dpi = 150

* Reproduce steps:
Install gnome-ring on a linux machine with a HiDPI display (e.g. 13 in. laptop with 1440p display)
Run gnome-ring

* Expected result:
gnome-ring renders on-screen elements at a larger scale in order to account for HiDPI display. This happens with all other applications such as qTox and Firefox.

* Actual result:
The user interface is rendered at an extremely small scale and is very hard to read. (most annoyingly so the message text is hard to read).