Update to latest v2 bootstrap

Downloaded from http://downloads.buildout.org/2/bootstrap.py
Fix nondeterministic test failures

This fixes three test failures I've seen on Python 3.3:

  test_allow_w_single_interface
  test_require_w_set_schema_normal_fields
  test_require_w_single_interface

All caused by dictionary iteration returning items in a different order
than the test expected.
Restore deprecated BBB imports of z.s.untrustedpython modules.
Prep 4.0.0a2 release.
svb
Fix test breakage under 4.0.0a2 due to deprecation strategy.
Prep 4.0.0a3 release.
svb
Fold in post-3.8.3, pre-4.0 changelog entries from release branches.
Try to make the tests pass on Windows
More tests are running under python-3

Include documentation doctests into main test suite. Documentation is
updated to be valid under python-3 and some critical bugs in python-3
are revealed.
Dictionary views are not proxied

Dict views for keys(), items(), and values() are not proxied, making
dicts work in python3 exactly as python2.
Use python3.3 to run documentation tests
Merge branch 'moretests'
Releasing 4.0.0a4
Python-3.3 compatibility for examples
- Remove ``untrustedpython`` extra again, since we do not want to support
  ``zope.untrustedpython`` in ZTK 2.0. If BBB is really needed, we will create
  a 3.10.0 release.
Make the CHANGES zest.releaser friendly and move TODOs to separate file.
Preparing release 4.0.0a4
Back to development: 4.0.0a5