Patched CakeResponse's MapType() to increase performance by reducing hun...

I have been doing so profiling to see why some of my requests were taking more processing time than i would like, and i found one of the bottlenecks to be on CakeResponse's mapType() method.
After discussing with rchavik on IRC about it, he came with this nice casting approach which saves around a thousand is_array() and is_string() system calls.

This screenshot shows that the method is about twice as fast now: http://i.imgur.com/ooAMwJC.png

// Diego