Add missing License file, apply coding standards and add static tests and travis configuration

[mhauri]

• add the LICENSE file because you refer to it in all php files
• apply coding standards
• add configuration for travis
• add static tests

In case you need help with setting up travis just tell me ;)

[osrecio]

Good PR! 😃

[mhauri]

Thank you @osrecio. Now waiting till @jalogut finds time to merge it 😉

[jalogut]

@mhauri there you go 🤙