updated readme

hakyll-bootstrap/README.md

-hakyll-bootstrap
+heakyll-bootstrap
 ================
 
 <p align="center" style="padding: 20px; width: 50%">
@@ -11,7 +11,7 @@ A template for a small corporate Hakyll site.
 
 ```bash
 $ stack build
-$ stack exec blog -- preview
+$ stack exec blog -- watch
 ```
 
 **Using cabal**