Check to see if wget is installed.
Merge pull request #8 from MarkBennett/handle-wget-not-installed

Check to see if wget is installed.
Ignore any EC2 instances that are not running

Previously plow was attempting to run on terminated and stopped
instances.
Merge pull request #11 from MarkBennett/only-run-on-running-instances

Ignore any EC2 instances that are not running