Add 'New Relic Cloudwatch Plugin' spot instance template

This [AWS CloudFormation](http://aws.amazon.com/cloudformation/) template starts a single [EC2 Spot Instance](http://aws.amazon.com/ec2/spot-instances/) via Auto Scaling from an upstream maintained EBS AMI of the [New Relic Cloudwatch Plugin](https://aws.amazon.com/marketplace/pp/B00DMMUO0O?sr=0-31&qid=1372405347838).