Bug Fixes and Other Changes
* disable Debugger defaults in unsupported regions
* modify session and kms_utils to check for S3 bucket before creation
* update docker-compose and PyYAML dependencies
* enable smdebug for Horovod (MPI) training setup
* create lib dir for dependencies safely (only if it doesn't exist yet).
* create the correct session for MultiDataModel
Documentation Changes
* update links to the local mode notebooks examples.
* Remove outdated badges from README
* update links to TF notebook examples to link to script mode examples.
* clean up headings, verb tenses, names, etc. in MXNet overview
* Update SageMaker operator Helm chart installation guide
Testing and Release Infrastructure
* choose faster notebook for notebook PR build
* properly fail PR build if has-matching-changes fails
* properly fail PR build if has-matching-changes fails