Replace AWS::ApiGateway::Deployment name on updates

[emilymdubois]

When I was updating the request template for the API Gateway passthrough method, I noticed that the method was not updating between CloudFormation updates. The updates only went into effect if I deleted and recreated the stack.

I think this can be avoided by creating a random resource name each time the stack is updated. This forces the original resource to be deleted, and the new resource to be created.

[davidtheclark]

I was also having StageName problems when trying to update the stack. Errors like this: 16:28:04Z us-east-1: CREATE_FAILED Deploymentbdcec9d2: StageDescription cannot be specified when stage referenced by StageName already exists. The way that I evaded these, in the end, was to use the random deployment name as part of the deployment's stage name — so it also changed with each update.

[rclark]

Closed by #10