Synchronous support for AFURLSessionManager

[paulmelnikow]

In the afn2 branch is a category for synchronous methods on AFHTTPRequestOperationManager.

It'd be good to add synchronous methods for AFURLSessionManager as well.

Perhaps we could use @floschliep's promising implementation: floschliep/NSURLSession-SynchronousTask

[floschliep]

Sure, go for it!

[paulmelnikow]

The 3.x implementation in 7d968ec includes support for AFHTTPSessionManager which may easily be backported to 2.x if there's a need.