DevEx API - WordPress-y version

[ashfame]

This PR offers a WordPress-y API for developers which leverages the Ops class itself introduced in #192 (and requires that PR be merged first)

This version is better than presented in #125 since this controls preview automatically.

To test this, I replaced the Ops::handle() calls from Transformer class' constructor and used:

add_action( 'data_liberated_' . SubjectType::BLOGPOST->value, array( $this, 'handler' ) );
add_action( 'data_liberated_' . SubjectType::PAGE->value, array( $this, 'handler' ) );

to achieve the same effect.

Closes #194