Fix font previews on OS X.
Fix font previews on OS X.

We accidentally wrapped the CFF private dict into an index, which is
not correct according to the spec. This made font previews fail on OS X.

We now just encode the DICT itself.

moyogo/opentype.js,fpirsch/opentype.js,Jolg42/opentype.js,fpirsch/opentype.js,axkibe/opentype.js,byte-foundry/opentype.js,Jolg42/opentype.js,brawer/opentype.js,nodebox/opentype.js,moyogo/opentype.js,byte-foundry/opentype.js,brawer/opentype.js,googlefonts/opentype.js,googlefonts/opentype.js,axkibe/opentype.js,nodebox/opentype.js