Fix all Corona examples to run

I switched so that all Corona examples use setAnimationByName instead of setAnimation. Without this fix, the goblin and dragon examples failed with the following error:

Runtime error
...e-runtimes/spine-corona/spine-lua/AnimationState.lua:171: attempt to index local 'animation' (a boolean value)
stack traceback:
	[C]: ?
	...e-runtimes/spine-corona/spine-lua/AnimationState.lua:171: in function 'setAnimation'
	...ona/spine-runtimes/spine-corona/examples/goblins.lua:25: in main chunk
	[C]: in function 'require'
	?: in function <?:982>
	(tail call): ?
	...nts/code/corona/spine-runtimes/spine-corona/main.lua:3: in main chunk