Update boostrap.py to the one for buildout 2.0

(Downloaded from http://downloads.buildout.org/2/bootstrap.py)

There seems to be a bug in buildout 2.0.0 where

  [python]
  recipe = zc.recipe.egg
  eggs = ${test:eggs}
  scripts =
  interpreter = python

ignores the 'interpreter' option and doesn't create a bin/python, just
because scripts is empty.  Setting scripts to a nonsense value works as
a workaround.