Unicode not handled in filenames in sidebar #124

(OSX, FWIW)

If I load an image in tev using, say,

$ tev 🐨.exr --hostname 192.168.86.70:6502

Then although the filename is correctly displayed in the title bar, it is not correct in the list of files in the sidebar.

(Not the most important bug ever, but more common characters like those with umlauts seem to have trouble as well...)