Rename exercises dir

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

topics/aws/exercises/no_application/exercise.md

@@ -0,0 +1,8 @@
+## No Application :'(
+
+### Objectives
+
+Explain what might be possible reasons for the following issues:
+
+1. Getting "time out" when trying to reach an application running on EC2 instance
+2. Getting "connection refused" error

topics/aws/exercises/no_application/solution.md

@@ -0,0 +1,21 @@
+## No Application :'(
+
+### Objectives
+
+Explain what might be possible reasons for the following issues:
+
+1. Getting "time out" when trying to reach an application running on EC2 instance
+2. Getting "connection refused" error
+
+### Solution
+
+1. 'Time out' Can be due to one of the following:
+
+  * Security group doesn't allow access
+  * No host (yes, I know. Not the first thing to check and yet...)
+  * Operating system firewall blocking traffic
+
+2. 'Connection refused' can happen due to one of the following:
+
+  * Application didn't launch properly or has some issue (doesn't listens on the designated port)
+  * Firewall replied with a reject instead of dropping the packets