Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/aws/exercises/create_user/exercise.md

@@ -0,0 +1,9 @@
+## IAM AWS - Create a User
+
+### Objectives
+
+As you probably know at this point, it's not recommended to work with the root account in AWS. For this reason you are going to create a new account which you'll use regularly as the admin account.
+
+1. Create a user with password credentials
+2. Add the newly created user to a group called "admin" and attach to it the policy called "Administrator Access"
+3. Make sure the user has a tag called with the key `Role` and the value `DevOps`