GlyphSet. A GlyphSet is simply a dict-like object mapping glyph names
to glyphs. The glyphs in a GlyphSet have a .draw(pen) method and a
.width attribute. This provides a generic interface for drawing glyphs
or extracting outlines, and works both for CFF-based fonts and TT fonts.
See also fontTools.pens.basePen for a description of what makes a Pen
a Pen.
git-svn-id: svn://svn.code.sf.net/p/fonttools/code/trunk@420 4cde692c-a291-49d1-8350-778aa11640f8