little bug fix for 2017-03-03-servant-and-db.markdown

Thank you for the post. Would you apply the patch, please.

```
$ git diff posts/2017-03-03-servant-and-db.markdown
diff --git a/posts/2017-03-03-servant-and-db.markdown b/posts/2017-03-03-servant-and-db.markdown
index 6c62dc2..dc181c7 100644
--- a/posts/2017-03-03-servant-and-db.markdown
+++ b/posts/2017-03-03-servant-and-db.markdown
@@ -134,7 +134,7 @@ app' :: Pool Connection -> Logger -> Application
app' pool logger = serve api $ hoistServer api nt $ createCat' :<|> readCat'
where
nt :: H x -> Handler x
- nt m -> runLogT "api" logger (runReaderT (runH m) pool)
+ nt m = runLogT "api" logger (runReaderT (runH m) pool)
```