Resize HImage's internal _image.

The internal _image (of type PImage) must be resized because certain HYPE funcationality depends on this internal image. An example is HPixelColorist which uses PImage's get function to retrieve the pixel color information. Therefore, without resizing _image, if you pass an HImage that has been resized into HPixelColorist, the pixel colors are retrieved from the original size and not the new size.

See the application of this fix in `examples/HPixelColorist/example_002/`. This pull request includes the newly compiled HYPE.pde, so if you'd like to see the previous behavior, then replace HYPE.pde in that example folder with a previously compiled version. If you do that, then you should observe that the underlying HPixelColorist's image is not resized to the new dimensions.