change setBindings to return the Builder object

Given how mergeBindings:
1. modifies the bindings
2. returns the builder object
I think it would be more consistent and useful for setBindings to also return the Builder object.

With the current code a user needs to do the following if they want to add bindings and execute a builder object:

	$builder = (/* builder object */);
	$builder->setBindings(array(...));
	$result = $builder->get();

With the proposed change the statement is simplified to the following:

	$result = (/* builder object */)->setBindings(array(...)->get();

Please also note that the proposed change is mostly backwards compatible given how most users would be using setBindings()