created a basic framework for DHL
generate DHL track request
TDD: added response validation and test casses for DHL status and destination
added DHL parsing for activities, status, location, service, weight,
destination, etc.
tweak DHL activity details
added status type checking and additional integration tests for DHL
updated readme for DHL
Merge pull request #4 from sailrish/dhl-client

Added a DHL Client to support DHL packages