Add AllowedPattern to Parameter (#968)
Add AllowedPattern to Parameter (#968)

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ssm-parameter.html#cfn-ssm-parameter-allowedpattern
johnctitus/troposphere,ikben/troposphere,ikben/troposphere,johnctitus/troposphere,pas256/troposphere,cloudtools/troposphere,cloudtools/troposphere,pas256/troposphere