v0.12.0

Added

• preview and tracer.Preview accept a boolean flag anti_alias to
  enable or disable anti-aliasing.

Changed

• preview and tracer.Preview enable anti-alisasing by default.
• Python, Cython, and C code must follow strict style guidelines.
• Renamed util.array to util.Array
• Renamed util.image_array to util.ImageArray
• Converted interact.SceneView.setScene to a property: scene

Removed

• preview and tracer.Preview no longer accept the aa_level
  argument
  • use anti_alias.