Chump

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- Reduce requests required to instantiate applications and users.
- Add connection pooling to improve network performance.
- Lazy evaluation of app and user authentication.
- Lazy evaluation of Application.sounds and User.devices.
- Improve compatibility with Python 2.7 through 3.7.
- Bugfixes.

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- Exception logging bugfixes.
- Dropped support for Python 2.6.
- General code formatting improvements.

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- Regression fixes.

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- Use unicode exclusively.
- Update length limits on message strings.
- Add support for HTML messages.
- Improve timezone support when pytz is unavailable.
- Remove requests dependency.
- Improve documentation.

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- Add new Pushover priority: LOWEST.
- Add Application.{limit,remaining,reset} to track message allotment.
- Fix title and message length validation.

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- Fix dependency issues when installing.