- the GlyphRecord object is getting messy. Look into
  consolidating all the various private reference attributes.
- the various private contextual attrs should be moved to properties.
- make the various Count attributes properties.


Not yet supported:
GSUB Lookup Type 8 (Reverse Chaining Context)
LookupFlag.RightToLeft

Skipped:
- should the glyph width be calculated into the glyph record's
  x-advance before returning it to the caller?
  - no. that is the responsibility of a render.
- need to handle featureRecord.FeatureParams if they exist (fontTools does not read these)
- make rand feature support smarter. look back through the
  processed glyphs and find the alternate that has occurred
  least frequently and farthest away. (this was skipped because
  the rand feature is not such a good idea to begin with)