Added

• PHP 7 goodness: declare(strict_types=1) and method return signatures
• PHP v7.3 tests in .travis.yml

Changed

• Made minimum requirement for PHP v7.1 (note: this is considered a compatible change)
• Updated to Carbon 2.0 (only affects tests)
• The $request and $options variables are now passed by reference in the retry callback to allow for modification (thanks @Krunch!)

Removed

• Removed unsupported tests for unsupported PHP versions from .travis.yml file
• Removed support for older versions of PHPUnit

Fixed

• Always ensure positive integer used when calculating delay timeout (fixes #12)
• Retry connect exception regardless of cURL error code (thanks @LeoniePhiline) (fixes #14)