Change pragma mark to correct protocol

Update a simple mis-labelling
Merge pull request #1809 from sevntine/patch-1

Change pragma mark to correct protocol
[Issue #1807] Updating documentation for manager reachability client
Merge branch 'master' of github.com:AFNetworking/AFNetworking
Using @selector instead of keys for associated objects
Fixing potential vulnerability caused by hard-coded multipary form data boundary. Thanks to Mathias Bynens & Tom Van Goethem for finding and disclosing this.

Signed-off-by: Mattt Thompson <m@mattt.me>