Fix: firefox settings save issue + trimmed fonts

* I fixed the problem @ELUTE reported with firefox displaying an error
when saving settings.
* Trimmed the font glyphs down to the 5 we are currently using.

Note: I discovered that you can “Import” the config.json into
fontello.com to start with the same list of fonts. Also, you can
overwrite /static/fonts when with the entire contents of the fontello
zip file to replace the font.