Move fallback country and currency to config
Create cacheControl helper function
Move geolocate related caching headers into the middleware
Switch to using new cacheControl helper
Enable some more cache header tests
More cache-control tests for ip determined locations
Grab exchange rates from openexchangerates.com, reduce accuracy to 2 dp and store for test suite
Normalise location of config
Create exchange wrapper, ensure that the path to JSON is stubbed
Load base and rates from the json
Add placeholders for etag tests
Create a convert method that will round to the correct number of decimal points for the target language.