Version 0.4.0 - The "Skip If" tag update

Added

• New Extension that adds a {% skip_if %} tag where you can insert any
  condition (e.g. checking the Context) and if it evals as True, a
  CancelRendering exception is raised and caught by the Renderers causing
  them to silently just skip rendering that template.
  • The StringRenderer returns None
  • The StoutRenderer prints out nothing
  • The FileRenderer doesn't create an output file
• Added unittests for the {% skip_if %} tag