Python-gyazo

- Out of beta!! 🎉
- Small internal improvements

- Fix `python_requires` in setup.py

Breaking Changes
- Remove `star` attribute from `Image` model 49
- Drop Python 3.3 support 50

Internal
- Improve type hints
- Update test environment 40 46
- Update libraries 41 44
- Improve versioning 42
- Improve packaging 43
- Refactoring 45 51

- Support Python 3.6 37
- Update CI environment 38 39

- Update upload API 34
- Introduce mypy-lang 30
- Add type hints 32 35
- Add more tests 33

- Remove gyazo-backup from python-gyazo 26
- gyazo-backup is moved to https://github.com/ymyzk/python-gyazo-backup
- Clean up setup.py 27
- Use Sphinx 1.4.x 28