Added recursion to concepts list.

app/locale/en.coffee

@@ -1212,6 +1212,7 @@
     variables: "Variables"
     vectors: "Vectors"
     while_loops: "While Loops"
+    recursion: "Recursion"
 
   delta:
     added: "Added"

app/schemas/models/level.coffee

@@ -34,6 +34,7 @@ defaultTasks = [
   'Write the guide.'
   'Write a loading tip, if needed.'
   'Click the Populate i18n button.'
+  'Add programming concepts covered.'
 
   'Mark whether it requires a subscription.'
   'Release to everyone via MailChimp.'

app/schemas/schemas.coffee

@@ -255,4 +255,5 @@ me.concept = me.shortString enum: [
     'variables'
     'vectors'
     'while_loops'
+    'recursion'
   ]