Update changelog to include hostname commit

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Runtime: Spawn shell within upstart script
 - Builder: Make sure ENV instruction within build perform a commit each time
 - Runtime: Handle ip route showing mask-less IP addresses
+- Runtime: Add hostname to environment
 
 ## 0.5.2 (2013-08-08)
  * Builder: Forbid certain paths within docker build ADD