Adds logging around image format

retain the buffer while processing

Removes empty method

Clear the image buffer when done

Adds vips clear cache

Sets more sane defaults, adds a mem stats method

Merge pull request davidbyttow#19 from mikestead/feature/compression-…

…and-lossless

Add support for compression and lossless options

Adds the ability to create an ImageRef from a VipsImage and set the I…

…mageRef for a transform

Only use bg color if set

Hooks up background color flattening