Merge remote-tracking branch 'brett/itsdangerous'

* brett/itsdangerous:
  Call is_updated instead of testing it boolean.
  Harden It's Dangerous key management.
  First tests for the Session class.
  Set a starting value for session.send_new_cookie.
  Remove beaker stuff from the code.
  Delete the session cookie on an empty session.
  Back sessions with It's Dangerous.
  Improve fs security for itsdangerous secret.
  Docs for get_timed_signer_url.
  Basic itsdangerous infrastructure.

Conflicts:
	mediagoblin/tests/test_cache.py

setup.py

@@ -43,7 +43,6 @@ setup(
     install_requires=[
         'setuptools',
         'PasteScript',
-        'beaker',
         'wtforms',
         'py-bcrypt',
         'pytest',
@@ -61,6 +60,7 @@ setup(
         'sqlalchemy>=0.7.0',
         'sqlalchemy-migrate',
         'mock',
+        'itsdangerous',
         ## This is optional!
         # 'translitcodec',
         ## For now we're expecting that users will install this from