Enable re-setting of fallback language and store it to redux state

[DimitrisD]

So far, the package is a great solution to add internationalization using react-redux. The only part that i found it to be missing was the multiple fallback languages.

Why is this a need?

Let's say that in an app, somebody wants to support multiple languages, with multiple dialects, and they want to have different fallback language for each of the dialects.

Right now, the redux-i18n doesn't support it.

Adding the newFallbackLanguage to the redux state, the functionality above is being added.

Somebody can set their initial fallback language the way they could, but using the function:
setFallbackLanguage(newfallback) they can have multiple fallbacks.

Usage:

import {setLanguage, setFallbackLanguage} from "redux-i18n"

componentWillMount() {
  // set of a dialect language
  this.props.dispatch(setLanguage("es-ES"))
  // set specific fallback to that language fallback
  this.props.dispatch(setFallbackLanguage("es"))
}

[francescarpi]

Thanks for your contribution!