Update to "getting started" content

[anamorph]

• updated README.md:

  • [best-practices] added possiblity to easily deploy in us-east-1, eu-west-1 and ap-southeast-2 regions.
  • [documentation] updated screenshots to reflect aws console changes for AWS CloudFormation & Amazon SageMaker.

• updated AWS CloudFormation template:

  • [documentation] all resources created are now documented in the template
  • [best-practices] now tagging all ressources to leverage AWS Systems Manager Application Manager.
  • [best-practices] now using ml.t3.medium instances vs ml.t2.medium previously; changed for newer regions compatibility.
  • [resource] new AWS CloudFormation Custom Resource to trigger AWS Lambda function BucketJanitor
  • [resource] new AWS Lambda Function BucketJanitor to empty bucket on Stack Deletion (previously not implemented and causing errors).
  • [resource] new AWS Systems Manager Parameters to pass variables securely to Amazon SageMaker Notebooks.
  • [resource] new AWS IAM Roles created directly in the AWS CloudFormation template to avoid typos and degraded Customer Experience.
  • [resource] new AWS IAM Policies created directly in the AWS CloudFormation template to avoid typos and degraded Customer Experience.
  • [best-practices] updated AWS IAM Policies created directly in the AWS CloudFormation template to reflect Security Best Practices: Principle of least privilege.

• updated getting_started/notebooks:

  • 1.Building_Your_First_Campaign.ipynb:
    • [best-practices] added a brief reminder of AWS's Shared Responsiblity model and pointed to Security Best Practices content. At AWS, security is our top priority.
    • [best-practices] removed all unnecessary AWS Account IDs.
    • [documentation] removed required inputs and replaced with calls to AWS Systems Manager.
    • [documentation] removed required creation of roles/policies as they are now created in AWS CloudFormation.
  • 3.Best_Practices-Clientside.ipynb:
    • [documentation] introduced AWS Systems Manager.
    • [documentation] updated bucket policy template features and to reflect Security Best Practices: Principle of least privilege.
    • [best-practices] added an optional security practice to enable Amazon S3 bucket Encryption in AWS Systems Manager Application Manager.
    • [best-practices] removed all unnecessary AWS Account IDs and sanitized sample outputs.
    • [best-practices] added an optional security practice to enable Amazon S3 bucket versioning with an Amazon CloudFormation template snipplet.

[annainspace]

I have reviewed this pull request, it is ready to be merged.