Duplicate code removed
Determine shipment size automatically for USPS
Merge https://github.com/pdt256/shipping

Conflicts:
	src/USPS/Rate.php
Merge https://github.com/pdt256/shipping
broken use removed
Added validation that all necessary properties are set
Setting all options in tests
Moving default values to __construct, because otherwise they get overwritten
Fixed formatting to match PSR-2
Merge pull request #9 from perk11/validation

Validation