Replace string comparison with instanceof test
Remove fast_path
Rename property classes and remove glyphspec from API
Now remove glyphspec altogether from property classes
Compute all_indices in GlyphView.set_data()
Call _map_data() on appropriate object
Access plot_view through renderer.plot_view
Access {x,y}mapper through renderer.{x,y}mapper
Glyph should ask its renderer for data source