fix fallback bug

[kilolumen]

Fix #465 #460

[PikachuEXE]

What does it archive?
I already added some test cases in #465

[kilolumen]

@PikachuEXE
old: locales = ["zh-Hans-TW", "zh", "zh-Hans", "en"]
fix: locales = ["zh-Hans-TW", "zh-Hans", "zh", "en"]

I18n.translations = {
    "zh": {
        "cat":  "貓" // Chinese Traditional
    },
    "zh-Hans": {
        "cat": "猫" // Chinese Simplified
    }
}

i18n.js line: 400

while (locales.length) {
      locale = locales.shift();
      scopes = fullScope.split(this.defaultSeparator);
      translations = this.translations[locale];
      // ....
}

Becuase shift() removes the first element from an array and returns it. so
old: Locale will assign "zh", and it will return "貓".
fix: Locale will assign "zh-Hans", and it will return "猫".

[PikachuEXE]

OK Please add a test case to ensure this fix is working

[kilolumen]

I already added a test case.

[PikachuEXE]

Thanks, will release soon

[PikachuEXE]

3.0.2 released (gem + npm)