Version 2.1

Minor fixes, including docs and compatibility list.
Miami-Dade County name is updated.

Version 2.0

Change to load counties according to state names rather than IDs. IDs have not
been consistent for many countries' states and provinces.

Counties have been moved to a separate JSON file for ease of reading the
extension and ease of applying the extension to other countries.

The county list has also been updated to reflect changes since it was compiled.

Version 1.1

Compatibility with 4.6 and 4.7 (no changes to code or counties)