Closes #35 Standarization of elcodi

* Added all entity providers, formatted and tested.
* Added all factory testing
* Moved all ReferralProgram model to entity namespace, as should be independent
of mapping logic
* Added twig dependency in CurrencyBundle and all elcodi project. Closes #81
* Fixed all code using php-cs-fixer

* Closes #69
* Closes #70
* Closes #71
* Closes #72
* Closes #73
* Closes #74
* Closes #75
* Closes #76
* Closes #77
* Closes #78
Replaced hhvm for hhvm.nightly in travis conf