Fix changelog formatting

CHANGELOG.md

@@ -8,8 +8,8 @@ Improvements:
 
 Bug Fixes:
  - Fix hypothetical race conditions on producer shutdown
-   ([#450](https://github.com/Shopify/sarama/pull/450)),
-   ([#451](https://github.com/Shopify/sarama/pull/451)).
+   ([#450](https://github.com/Shopify/sarama/pull/450),
+   [#451](https://github.com/Shopify/sarama/pull/451)).
 
 #### Version 1.4.0 (2015-05-01)