- use inlined getargspec

- The "output encoding" now defaults
  to "ascii", whereas previously
  it was set to None.  This has the effect
  of FastEncodingBuffer being used internally
  by default when render() is called, instead
  of cStringIO or StringIO, which are
  slower, but allow bytestrings with
  unknown encoding to pass right through.
  It is of course not recommended to use
  bytestrings of unknown encoding. Usage of
  the "disable_unicode" mode also requires
  that output_encoding be set to None.