docs(README): update docs and website url (#30)

Author: McSneaky

README.md

@@ -21,11 +21,11 @@
 
 <div align="center">
   <h3>
-    <a href="https://preview.adonisjs.com">
+    <a href="https://adonisjs.com">
       Website
     </a>
     <span> | </span>
-    <a href="https://preview.adonisjs.com/guides">
+    <a href="https://docs.adonisjs.com/guides/installation">
       Guides
     </a>
     <span> | </span>