updated user tracking to affected user tracking

README.md

@@ -138,7 +138,7 @@ If true is passed in, and **$useAsyncSending** is set to *false*, client->SendEx
 
 You can transmit the version number of your PHP project along with the message by calling `SetVersion()` on your RaygunClient after it is instantiated - this is optional but recommended as the version number is considered to be first-class data for a message.
 
-### User tracking
+### Affected user tracking
 
 **New in 1.5: additional data support**
 
@@ -233,4 +233,4 @@ If, when running a PHP script from the command line on *nix operating systems, y
 - 1.2.1: Several bugfixes for user tracking and request processing
 - 1.2: Added new async sending function; removed cURL dependency
 - 1.1: Added user tracking support; improved experience in CLI mode; add user-specified timestamp support; fixed user data encoding error
-- 1.0: Initial commit
+- 1.0: Initial commit