Support dot in localized keys

[rmariuzzo]

This issue was originally reported at: rmariuzzo/Laravel-JS-Localization#115 by @ERPedersen.

The following test will not work:

it('should return the expected message if the key has a dot', function() {
  expect(lang.get('messages.dot.in.key')).toBe('Dot In Key');
})

By default, Lang.js interpret . as separators. Therefore, we would to detect if a key exist with the dot.

Steps to reproduce

1. git clone https://github.com/rmariuzzo/Lang.js
2. git checkout develop
3. npm run test

Tasks

• Support simple dot key.
• Support nested dot key.
• Support tricky dot key.