add unicode-range test

fixes #1058

This test embeds a base64'd truetype font with two characters, the `<space>` and `m` specifically, specifying the unicode-range to only use the `<space>` (U+002E) . It then creates four elements, two of each, one with the font and without, adds them to the DOM, and check their width. If the space changes width, and the m doesn't, then we have a winner.