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:sparkles: Added
- Added IAM User assertions: `has.name`, `was.created_at`, `belongs_to.group`
- Added IAM Policy assertions: `has.name`, `has.description`, `was.created_at`, `was.last_updated_at`, `should_be.attached_to`
- Added IAM Group assertions: `has.name`, `was.created_at`, `should.contain`, `has.policy`
- Added IAM Role assertions: `has.name`, `has.description`, `was.created_at`, `was.last_used_on`, `uses.policy`
- Added SNS Topic assertions: `should.receive`
:pencil2: Changed
- `s3.Bucket.should.contain()` now accepts `s3.Object` as an alternative to a `str` key
- assertions now `assert` themselves rather than returning a `bool`
- Added better `AssertionError` messages