Adapting readme to workshop and quick-fixes to notebooks

[mttanke]

Issue #, if available:

Description of changes: Adapting Readme to workshop documentation Quick fixes to notebooks including:

• Adding comment to notebook 1 for notifying user that Athenas query is still being executed
• Removing ml.t2.medium instance types
• Renaming model variable to xgboost
• Adding training and deployment pipelines documentation

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