Added Laravel 5.7 support

Added support for Laravel 5.7

Relates to #1

Fire an event on synchronisation completion

Added

• Event class
• Event test case
• Fire the event in the command

Behaviour

Once the synchronisation command is completed an event will be fired. With an event listener you'll than be able to clear your translation caches or something else that involves the locales / translations.

Locales file

Added

• Create a resources/lang/locales.json file so you have all the available locales.
• Added unit tests to test the locales functionality.

Changed

• Abstracted the JSON file creation in the command to a separate function.

Initial working code!

Added

• Retrieve all languages of a project of the POEditor API
• Retrieve all terms of a project of the POEditor API
• Store the terms in a Laravel compatible JSON file
• Support for trans_choice in combination with the POEditor plural feature