Modern-shippo

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**Minor Improvements**

- Fix relative imports for Python 3

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**Minor Improvements**

- Only show DeprecationWarning for shippo package.

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**Bugfixes**

- add version to shippo

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**Improvements**

- Removed polling for shipments and transactions calls
- Fixed and added tests

**Behavioural Changes**

- [WARNING] Changed keyword for creating shipments and transactions synchronously from `sync=True` to `async=False`

**Minor Improvements**

- Added fixtures to our tests using vcr
- Added Travis-CI
- Added badges to the README
- Bumped unittest version

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