Rename exercises dir

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

topics/aws/exercises/asg_dynamic_scaling_policy/exercise.md

@@ -0,0 +1,16 @@
+## AWS Auto Scaling Groups - Dynamic Scaling Policy
+
+### Requirements
+
+1. Existing Auto Scaling Group with maximum capacity set to at least 3
+2. One running EC2 instance with max of 4 CPUs
+
+### Objectives
+
+1. Create a dynamic scaling policy with the following properties
+  1. Track average CPU utilization
+  2. Target value should be 70%
+2. Increase the CPU utilization to at least 70%
+  1. Do you see change in number of instances?
+1. Decrease CPU utilization to less than 70%
+  1. Do you see change in number of instances?