Fix bug in CSRF state persistence when using shared sessions.
BaseFacebook loads the stored state in its constructor. However, at
that point, the shared session ID has not yet been initialized, so
getPersistentData() will return data from the non-shared-session cookie. Since
initSharedSession() depends upon state initialized in
BaseFacebook::__construct, just re-initialized the stored
state in the shared session situation.

Added appropriate tests to check CSRF state persistence with and without shared sessions.
Make getLoginStatusUrl use /dialog/oauth

To make this a drop in replacement for the old endpoint, we also need
support from the /dialog/oauth endpoint. Specifically, the current
endpoint, when using display=none, always return the response as part of
the fragment, while the PHP SDK needs the signed_request as a query
string argument.
Merge pull request #59 from JohnnyGoods/master

Fix bug in CSRF state persistence when using shared sessions.
Merge pull request #94 from oyvindkinsey/master

Make getLoginStatusUrl use /dialog/oauth
Merge upstream/master