Gracefully handle HTTP Errors on font file references

[nickfujita]

When providing a reference to a font file as a part of options, it was find that in the case where for some reason there was an error retrieving said file, the library errors out. Rather than having this prevent the subs from rendering at all, would it be possible to instead handle this gracefully, by not erroring out, and just render any subs with the default library font?

[nickfujita]

Just wanted to ping for any feedback. I've been trying over and over to get this repo compiling on my local machine (OSX) but always receiving errors when patching. As detailed here