Introduce Bindable trait

Bindable introduces the next feature: dynamic data binding.

Full code coverage

Now that this repository has been prototyped, it has reached full test coverage. Let's keep it at 100% as new features are introduced.

Documentation started

The readme file touches on the three main features of the library: binding, custom elements and template elements.

Expand nested components

Components can contain components. This is now implemented and tested, but may change.

Custom components

Custom components are now automatically converted into their template HTML.

Basic DOM extension

This first pre-release marks the successful extension of PHP.Gt/Dom with extended behaviour.