Added from_country, to_country, commercial and packaging arguments
to get_transit_time and get_rate methods
Tests for international rates and times
Changed connection timeout
Changed carrier to make test passing.

Shipment was at first created using test credentials and got some random
tracking number, then we tried to track this number, and got "Invalid
tracking number". This was fixed by changing carrier to USPS, as it
returns valid data for the random tracking number it issues to test
shipments.
Merge pull request #15 from stxnext/117672_international

[117672] International rates and times