changed code block syntax in renamed metadata episode

Author: Toby Hodges

_episodes/17-metadata.md

@@ -25,9 +25,10 @@ and workflows. This example includes metadata allowing others to cite your tool.
 
 *metadata_example2.cwl*
 
-```
+~~~
 {% include cwl/metadata_example2.cwl %}
-```
+~~~
+{: .source}
 
 #### Extended Example
 
@@ -38,8 +39,9 @@ requirements in order to use the tool, and a few more metadata fields.
 
 *metadata_example3.cwl*
 
-```
+~~~
 {% include cwl/metadata_example3.cwl %}
-```
+~~~
+{: .source}
 
 [schema-salad]: http://www.commonwl.org/v1.0/SchemaSalad.html#Explicit_context