Few formatting improves

Merged #3, resolved #2.

Improvements in price formatting

Slightly improved searching of an appropriate locale for price formatting.
It looks like on iOS 13 there might be several locales for specific currency codes and unluckily, the old code may choose the wrong locale. So, we try to find the locale in which currencySymbol differs from currencyCode first.
For example, for RUB we have these locales with RUB currencyCode:
[ba_RU, ru_RU, cv_RU, sah_RU, ce_RU, myv_RU, tt_RU, os_RU, en_RU]
but if we take a look at it's currencySymbol, we see:
"RUB", "₽", "RUB", "₽", "₽" ,"RUB", "₽", "₽", "RUB"

So, since now the library will peek ru_RU locale, since it has more friendly currency formatting.

Swift 5

• Example upgrade to swift 5
• Added conformance to Hashable and Equatable

Initial release

Initial library release