Changed to PSR-4 class loader.
Renamed folders "Cake" to "src" and "Test" to "tests".
Fixed travis config.
Merge pull request #2632 from ADmad/3.0-psr4-loader

Changed to PSR-4 class loader.
Fixed path to cake console executable.
Very basic Radio input rendering started.
Add support for complex input type format.
Add checked + disabled support to radio buttons.
Add support for custom labels.

You can both disable and customize all of the labels with additional
properties.
Add tests for usage of radioContainer.
Add empty option support.

Add the empty option that FormHelper currently supports.
Move files to match 3.0 directory moves.