Add LICENSE file

[siwinski]

No description provided.

[siwinski]

This pull request is just adding a LICENSE text file. The test failure is Travis' build of PHP 5.3.3 which is not compiled with openssl so the following error occurs on composer run:

  [Composer\Exception\NoSslException]                                          
  The openssl extension is required for SSL/TLS protection but is not availab  
  le. If you can not enable the openssl extension, you can disable this error  
  , at your own risk, by setting the 'disable-tls' option to true.    

[JakubOnderka]

Merged 👍 Thank you and Travis build is now fixed also for PHP 5.3.3.