vectors and also generally cleaned up the code a bit.

inputs it would sometimes produce a reflection rather than a similarity
transform.

matrices are singular even after performing PCA.

dimension.

tools.

an image when an empty rectangle is supplied.  Previously, it just
did nothing to the image in this case.

particular, this change allows complex valued images to be the output of
extract_image_chips().

API.  Also made find_candidate_object_locations() correctly include any
input boxes in the call to the C++ version of the function.

on some newer OS X installs.

are supposed to since, on some systems, these libraries aren't installed
correctly and will cause linker errors if used.

incorrect outputs when the requested chip stretched the image unevenly
vertically or horizontally.  This is because we used the best similarity
transform rather than affine transform between the image and the output chip.

certain compiler errors you get when accidentally trying to mutate
a const image a little easier to understand.

Also just cleaned up a few minor details.

I changed the spec to reflect this.