Update Flavours.rb with new M3 Instance Types

*Accouncement*: http://aws.typepad.com/aws/2014/01/aws-update-new-m3-features-reduced-ebs-prices-reduced-s3-prices.html
*Instance Types*: http://aws.amazon.com/ec2/instance-types/
Merge pull request #2618 from gaurish/patch-1

Update AWS flavors with new M3 Instance Types