Adding session_start() to the initialization docs.

Saves lots of troubleshooting (mainly when people are testing the API alone, without any framework or complete setup behind). See http://stackoverflow.com/questions/23522583/facebooksdkexception-session-not-active-could-not-store-state
Merge pull request #236 from leonelsr/patch-1

Adding session_start() to the initialization docs.
At least one endpoint allows for the type parameter to be set in the URL (paginated responses for example). If we're making a request to a URL with 'type' already specified, we don't need to include it as a query parameter
Merge pull request #242 from asolberg/next_request_type_path_conflict

At least one endpoint allows for the type parameter to be set in the URL...
FacebookRedirectLoginHelper::getReRequestUrl
getReRequestUrl: state restored
getReRequestUrl: state removed again
Merge pull request #243 from urmaul/4.0-dev

FacebookRedirectLoginHelper::getReRequestUrl
add `getEmail()` method to `Facebook::GraphUser()`

Tested and working in my application.
Merge pull request #253 from r3wt/4.0-dev

add `getEmail()` method to `Facebook::GraphUser()`
Updating default Graph API version to 2.2
Merge pull request #255 from facebook/gFosco.graph-v2.2

Updating default Graph API version to 2.2