Add ability to load a file from local bundle instead

[morgz]

Using this library with SPM will not bring in the resources (those lovely little json files)

I've added an alternative initializer where you can specify a path.

e.g

let locale = "en"
let stringPath = Bundle.main.path(forResource: locale, ofType: "json")
let faker = Faker(locale: locale, path: stringPath!)

BEFORE this is considered merge worthy...

• Can only load base translation files: 'en, es, ru, etc...' Trying to load a .json with "-" will fail (en-GB) I couldn't be bothered yet to step through the parser to find where it loads the "en" after loading the extras from "en-gb"
• I added some simple tests but better if the creator can review and amend to properly cover.