Fix typo in readme sample

Author: Pascal Berger

README.md

@@ -67,7 +67,7 @@ Use [stack-generator](https://github.com/stacktracejs/stack-generator) to genera
 * **offline: Boolean (default: false)** - Set to `true` to prevent all network requests
 
 #### `StackTrace.instrument(fn, callback, /*optional*/ errback)` => Boolean
-Call callback with a _stack trace_ anytime `interestingFn` is called. Returns `true` if given Function is successfully instrumented
+Call callback with a _stack trace_ anytime `fn` is called. Returns `true` if given Function is successfully instrumented
 * **fn** - Function to wrap, call callback on invocation and call-through
 * **callback** - Function to call with stack trace (generated by `StackTrace.get()`) when fn is called
 * **errback** - (Optional) Function to call with Error object if there was a problem getting a stack trace.