Add some integration tests

The included images are taken from the libtiff test suite.

tests/images/COPYRIGHT

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+Copyright (c) 1988-1997 Sam Leffler
+Copyright (c) 1991-1997 Silicon Graphics, Inc.
+
+Permission to use, copy, modify, distribute, and sell this software and 
+its documentation for any purpose is hereby granted without fee, provided
+that (i) the above copyright notices and this permission notice appear in
+all copies of the software and related documentation, and (ii) the names of
+Sam Leffler and Silicon Graphics may not be used in any advertising or
+publicity relating to the software without the specific, prior written
+permission of Sam Leffler and Silicon Graphics.
+
+THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
+EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
+WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
+
+IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
+ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
+OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
+LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
+OF THIS SOFTWARE.

tests/images/README.txt

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+The test files in this directory mostly have dimension 157x151.
+The naming convention is
+
+   photometric-channels-bits.tiff
+
+minisblack-1c-16b.tiff
+minisblack-1c-8b.tiff
+miniswhite-1c-1b.tiff
+palette-1c-1b.tiff
+palette-1c-4b.tiff
+palette-1c-8b.tiff
+rgb-3c-16b.tiff
+rgb-3c-8b.tiff
+
+logluv-3c-16b.tiff: logluv compression/photometric interp
+minisblack-2c-8b-alpha.tiff: grey+alpha
+
+BMP files (anchient BMPv2 since v3 does not work):
+
+  palette-1c-8b.bmp
+  rgb-3c-8b.bmp
+
+GIF files (anchient GIF '87 since modern GIF does not work):
+  palette-1c-8b.gif
+
+PNM files:
+  minisblack-1c-8b.pgm
+  miniswhite-1c-1b.pbm
+  rgb-3c-8b.ppm