Watchtower

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- Create log streams lazily (97)

- Test and package infrastructure improvements

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- Bug fix on log group retention (80)

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Fix another Homebrew-related release failure

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- Re-release 0.7.0 due to Homebrew-related automation failure

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- Add put_retention_policy (79)

- Add create_log_stream (77)

- Minor test and doc improvements

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- Set creating_log_stream to False when creation fails. (72)

- Define all instance attributes before attempting to create boto
session (76)

- Serialize objects with datetimes, and allow custom serializer default
functions to be used (73)