Rename exercises dir

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

topics/shell/solutions/host_status.md

@@ -0,0 +1,20 @@
+## It's Alive!
+
+### Objectives
+
+1. Write a script to determine whether a given host is down or up
+
+### Solution
+
+```
+#!/usr/bin/env bash
+SERVERIP=<IP Address>
+NOTIFYEMAIL=test@example.com
+
+ping -c 3 $SERVERIP > /dev/null 2>&1
+if [ $? -ne 0 ]
+then
+   # Use mailer here:
+   mailx -s "Server $SERVERIP is down" -t "$NOTIFYEMAIL" < /dev/null
+fi
+```