Series of changes for the tiff encoder:

 * Added configuration options for the TIFF encoder. The options are:
   - compression: adobe_deflate(default), deflate, lzw, none
   - zlevel: 0-9
   - scanline: 1,0 (Forces scanline encoding)
 * Fixed bug in encoder with scanline where memory was being modified
 * by TIFFWriteScanline. A buffer is now created for each row to prevent
 * modification of the underlying image_data.
A small modification to the image_tests removing some options not indended to be left on