Export the parse and createCurrencyFormat function

[johnny-dash]

In our situation, we don't want to register the plugin globally as most of the pages are not using it. Therefore we go with directive solution which allows you to import this currency input on demand. However, this means we need to implement our own parseCurrency method and we can't config the default currency and locale (The default locale configuration is passed in as a parameter when the library is registered globally). When we creating our own parseCurrency function, we find that parse and createCurrencyFormat in the parseCurrency implementation is not exported. This pull request is to export these two functions so we can create our own parseCurrency function

[johnny-dash]

The pull request here is to fix the issue: #27

[dm4t2]

Hi, thanks for contributing, but the functions parse and createCurrencyFormat are not intended to be part of the public API. I will provide a appropriate solution to allow parsing without global Vue plugin installation.