use buildout to build so we don't have 2 environments to manage

This is also a workaround for pypa/setuptools#864, since the default pypy3 on
Travis is quite old.

(cherry picked from commit def73970
                       and 5dcca55e)

.travis.yml

@@ -8,25 +8,12 @@ python:
     - 3.4
     - 3.5
 install:
-    # First install a newer pip so that it can use the wheel cache
-    # (only needed until travis upgrades pip to 7.x; note that the 3.5
-    # environment uses pip 7.1 by default).
-    - travis_retry pip install -U pip
-    # A newer wheel is also needed under Python 3, but only after we have
-    # a newer pip to take advantage of the cache.
-    - travis_retry pip install -U wheel
-    # Then start installing our deps so they can be cached. Note that use of --build-options / --global-options / --install-options
-    # disables the cache.
-    - travis_retry pip install -U manuel zope.testing zope.testrunner
-    - travis_retry pip install -U -e .
+    - pip install zc.buildout
+    - buildout
 script:
-    - zope-testrunner -u --test-path=src --auto-color --auto-progress
-    - zope-testrunner -f --test-path=src --auto-color --auto-progress
+    - bin/test -v1j99
 notifications:
     email: false
-# cache: pip seems not to work if `install` is replaced (https://github.com/travis-ci/travis-ci/issues/3239)
 cache:
   directories:
-    - $HOME/.cache/pip
-before_cache:
-    - rm -f $HOME/.cache/pip/log/debug.log
+    - eggs