Dev notes for master branch.

[futhr]

After some refactor on master branch I noticed a lot that can be improved:

• Change currency display wrong price format due to Spree Core has general settings options for this based on single currency usage. This should be changed in Core to fetch format from Money.
• Automatic update functionality like optional automatic conversion from base currency. #16. This functionality also exist in a diverted repository https://github.com/pronix/spree-multi-currency but no clue on its state.
• Validate that general config settings support multiple stores.
• Ensure it show per default correct currency related to language, this is probably harder then it sounds and probably need to add default currency value to countries. Or maybe just Money::Currency.find_by_iso_numeric will do the trick.
• Need to look into issue Bind Payment Methods to Currency #23

These are dev memory notes, you welcome to help out with PR if you find it valid.