Adding system tests to make sure token exchange works as expected.

- Updates CONTRIBUTING.md to explain how to set-up and run these tests.
- Requires a version of httplib2 that has not been released on PyPI
  yet in order to work on Python 3.
- Simply creates 3 different token types (JSON key for svc. acct.,
  P12 key for svc. acct., JSON key for user acct.) and then authorizes
  an httplib2.Http object to hit the USERINFO API.

1 files changed, 1 insertions, 1 deletions

diff --git a/setup.py b/setup.py
index 2e48f11..e0cf61e 100644
--- a/setup.py
+++ b/setup.py
@@ -35,7 +35,7 @@ packages = [
 ]
 
 install_requires = [
-    'httplib2>=0.8',
+    'httplib2>=0.9.1',
     'pyasn1==0.1.7',
     'pyasn1_modules==0.0.5',
     'rsa==3.1.4',