Implement update_stack

[Harper04]

ex_aws_cloudformation is currently missing:
https://docs.aws.amazon.com/AWSCloudFormation/latest/APIReference/API_UpdateStack.html

Could be useful together with create delete and cancel_update

[benwilson512]

PR welcome!

[Aduril]

I have the same issue.

I see @Harper04 provided a PR: #4
Merge, plz? :)

[baruchlubinsky]

I think that PR should have a version bump. Should I create a new one to do that?

[Aduril]

@benwilson512
Can you please upgrade the version, so that this will be available via hex? :)
Thanks!

For the time now, if someone wants to use the changes from the PR, import it into your mix.exs by

  def project do
    [
     ...,
     deps: [
       ..., 
       {:ex_aws_cloudformation, [ git: "https://github.com/ex-aws/ex_aws_cloudformation.git", ref: "8fe8ceb62ab9d018a572038387fe98f3ffdc4212" ]},
       ...
    ],
    ...
  ]