Fix PHPUnit suite configuration (#6)

Add PHP 7.2

Fix tokenizer returning lower case outward/inward codes, and testing …

…against lower case postcodes

Add build status and coverage badges

Fix license

Removed unnecessary Guzzle use statements

Completed support for PostcodeAnywhere and refactored to use custom A…

…ddress object

Correct reference to inward

Added docs for retrieving outward and inward codes

Return correctly when getting by environment