Fixed chapter chain

Froussios · Froussios · commit b01d954d8323 · 2015-04-26T21:15:28.000+02:00
diff --git a/Part 4 - Concurrency/1. Scheduling and threading.md b/Part 4 - Concurrency/1. Scheduling and threading.md
@@ -343,4 +343,4 @@ Again on 11
 
 | Previous | Next |
 | --- | --- |
-| [Hot and cold observables](/Part 3 - Taming the sequence/6. Hot and Cold observables.md) | [Testing Rx](/Part 4 - Concurrency/2. Testing Rx.md) |
+| [Custom operators](/Part 3 - Taming the sequence/7. Custom operators.md) | [Testing Rx](/Part 4 - Concurrency/2. Testing Rx.md) |
