Document IAM permissions needed

[dankantor]

The IAM user executing this will need certain permissions. We should list these in the docs somewhere.

[dankantor]

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowAccessToIAM",
            "Effect": "Allow",
            "Action": [
                "iam:GetUser"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Sid": "AllowAccessToAPIGateway",
            "Effect": "Allow",
            "Action": [
                "apigateway:GET",
                "apigateway:POST"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Sid": "AllowAccessToLambda",
            "Effect": "Allow",
            "Action": [
                "lambda:GetFunction",
                "lambda:CreateFunction",
                "lambda:UpdateFunctionCode",
                "lambda:UpdateAlias"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}