Merge pull request #67 from common-workflow-language/manabuishii-patch-1

Fix #66 missing link for recommended practices

Author: mr-c

_episodes/13-expressions.md

@@ -80,4 +80,4 @@ You can only use expressions in certain fields.  These are:
 - `outdirMax`
 
 [file-prop]: http://www.commonwl.org/v1.0/CommandLineTool.html#File
-[rec-practices]: /rec-practices/
+[rec-practices]: http://www.commonwl.org/user_guide/rec-practices/