Switching the test runner to py.test

This is the first step in moving to py.test.

* Created `scripts/run-tests.py` that handles invoking `py.test` for all samples.
* Updated `tox.ini` to use `scripts/run-tests.py` for the `{py27,py34}{-all}` environments.
* Removed all unneeded `__init__.py` files. The repository is now a loose collection of independent packages instead of being one monster package.
* Created `appengine/conftest.py` to do what nosegae used to do in terms of import/dev_appserver magic.

Outstanding questions/issues:
* Currently pytest arguments are specified in `tox.ini`. Not sure if we want to move those into `run-tests.py` or not.

After this is merged, I can look into converting our tests from `unittest` style to `py.test` style, which is generally cleaner.

Author: Jon Wayne Parrott

.gitignore

@@ -16,3 +16,5 @@ lib
 testing/resources/test-env.sh
 testing/resources/service-account.json
 secrets.tar
+.cache
+junit.xml

.travis.yml

@@ -19,9 +19,10 @@ before_install:
 - openssl aes-256-cbc -k "$secrets_password" -in secrets.tar.enc -out secrets.tar -d
 - tar xvf secrets.tar
 install:
-- pip install tox
+- pip install tox coverage
 - pip install -e git+https://github.com/GoogleCloudPlatform/python-repo-tools#egg=python-repo-tools
 - gcp-python-repo-tools download-appengine-sdk `dirname "${GAE_PYTHONPATH}"`
 script:
 - source ${TRAVIS_BUILD_DIR}/testing/resources/test-env.sh
 - tox
+- coverage report

appengine/__init__.py

@@ -12,11 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import main
 from testing import AppEngineTest
 import webtest
 
-from . import main
-
 
 class TestAppIdentityHandler(AppEngineTest):
     def setUp(self):

appengine/app_identity/__init__.py

@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 # [START all]
 
 """

appengine/app_identity/signing/__init__.py

@@ -15,12 +15,11 @@
 import re
 
 from apiclient.http import HttpMock
+import main
 import mock
 import testing
 import webtest
 
-from . import main
-
 
 class TestAuthSample(testing.AppEngineTest):