add link to stack overflow answer

The answer on how to write to a file from a heredoc

Author: cesc1989

aws/install_and_configure_awscli.sh

@@ -6,6 +6,7 @@ mkdir ~/.aws
 
 touch ~/.aws/config
 
+# Taken from https://stackoverflow.com/a/17093489/1407371
 tee ~/.aws/config <<- EOF > /dev/null
 [default]
 region=us-east-1