changed default behavior of SESSION_EXPIRATION setting

I ran tests, and they failed, but I /think/ it's for unrelated reasons:

(venv)~/workspace/python-social-auth$ ./run_tox.sh 
GLOB sdist-make: /Users/pyrak/workspace/python-social-auth/setup.py
py26 create: /Users/pyrak/workspace/python-social-auth/.tox/py26
py26 installdeps: -r/Users/pyrak/workspace/python-social-auth/social/tests/requirements.txt
py26 inst: /Users/pyrak/workspace/python-social-auth/.tox/dist/python-social-auth-0.2.0-dev.zip
py26 runtests: PYTHONHASHSEED='2566728021'
py26 runtests: commands[0] | nosetests --where=social/tests --stop
.....................................................................................................................E
======================================================================
ERROR: test_login (social.tests.backends.test_google.GoogleOpenIdTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/test_google.py", line 253, in test_login
    self.do_login()
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/base.py", line 63, in do_login
    user = self.do_start()
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/open_id.py", line 119, in do_start
    return self.backend.complete()
  File "/Users/pyrak/workspace/python-social-auth/social/backends/base.py", line 40, in complete
    return self.auth_complete(*args, **kwargs)
  File "/Users/pyrak/workspace/python-social-auth/social/backends/open_id.py", line 170, in auth_complete
    self.process_error(response)
  File "/Users/pyrak/workspace/python-social-auth/social/backends/open_id.py", line 178, in process_error
    raise AuthFailed(self, data.message)
AuthFailed: Authentication failed: Nonce already used or out of range
-------------------- >> begin captured logging << --------------------
requests.packages.urllib3.connectionpool: INFO: Starting new HTTPS connection (1): www.google.com
requests.packages.urllib3.connectionpool: DEBUG: "POST /accounts/o8/ud?source=mail HTTP/1.1" 200 1413
--------------------- >> end captured logging << ---------------------

----------------------------------------------------------------------
Ran 118 tests in 2.466s

FAILED (errors=1)
ERROR: InvocationError: '/Users/pyrak/workspace/python-social-auth/.tox/py26/bin/nosetests --where=social/tests --stop'
py27 create: /Users/pyrak/workspace/python-social-auth/.tox/py27
py27 installdeps: -r/Users/pyrak/workspace/python-social-auth/social/tests/requirements.txt
py27 inst: /Users/pyrak/workspace/python-social-auth/.tox/dist/python-social-auth-0.2.0-dev.zip
py27 runtests: PYTHONHASHSEED='2566728021'
py27 runtests: commands[0] | nosetests --where=social/tests --stop
.....................................................................................................................E
======================================================================
ERROR: test_login (social.tests.backends.test_google.GoogleOpenIdTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/test_google.py", line 253, in test_login
    self.do_login()
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/base.py", line 63, in do_login
    user = self.do_start()
  File "/Users/pyrak/workspace/python-social-auth/social/tests/backends/open_id.py", line 119, in do_start
    return self.backend.complete()
  File "/Users/pyrak/workspace/python-social-auth/social/backends/base.py", line 40, in complete
    return self.auth_complete(*args, **kwargs)
  File "/Users/pyrak/workspace/python-social-auth/social/backends/open_id.py", line 170, in auth_complete
    self.process_error(response)
  File "/Users/pyrak/workspace/python-social-auth/social/backends/open_id.py", line 178, in process_error
    raise AuthFailed(self, data.message)
AuthFailed: Authentication failed: Nonce already used or out of range
-------------------- >> begin captured logging << --------------------
requests.packages.urllib3.connectionpool: INFO: Starting new HTTPS connection (1): www.google.com
requests.packages.urllib3.connectionpool: DEBUG: "POST /accounts/o8/ud?source=mail HTTP/1.1" 200 1413
--------------------- >> end captured logging << ---------------------

----------------------------------------------------------------------
Ran 118 tests in 2.336s

FAILED (errors=1)
ERROR: InvocationError: '/Users/pyrak/workspace/python-social-auth/.tox/py27/bin/nosetests --where=social/tests --stop'
py33 create: /Users/pyrak/workspace/python-social-auth/.tox/py33
ERROR: InterpreterNotFound: python3.3
py34 create: /Users/pyrak/workspace/python-social-auth/.tox/py34
ERROR: InterpreterNotFound: python3.4
doc create: /Users/pyrak/workspace/python-social-auth/.tox/doc
doc installdeps: sphinx
doc inst: /Users/pyrak/workspace/python-social-auth/.tox/dist/python-social-auth-0.2.0-dev.zip
doc runtests: PYTHONHASHSEED='2566728021'
doc runtests: commands[0] | sphinx-build -b html -d /Users/pyrak/workspace/python-social-auth/.tox/doc/tmp/doctrees . /Users/pyrak/workspace/python-social-auth/.tox/doc/tmp/html
Making output directory...
Running Sphinx v1.2.2
loading pickled environment... not yet created
loading intersphinx inventory from http://docs.python.org/objects.inv...
building [html]: targets for 97 source files that are out of date
updating environment: 97 added, 0 changed, 0 removed
reading sources... [100%] use_cases                                                       
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [100%] use_cases                                                        
writing additional files... (0 module code pages) genindex search
copying static files... done
copying extra files... done
dumping search index... done
dumping object inventory... done
build succeeded.
________________________________________ summary _________________________________________
ERROR:   py26: commands failed
ERROR:   py27: commands failed
ERROR:   py33: InterpreterNotFound: python3.3
ERROR:   py34: InterpreterNotFound: python3.4
  doc: commands succeeded