Fixing issue for CUDA feautre extraction (#117)

Using THROW_CHECK_EQ(options_.max_image_size, sift_gpu->GetMaxDimension()); causes issues for me when using CUDA as I don't seem to be able to set the parameter right. It seems wrong to me to expect that max_image_size is set to GetMaxDimension, as the latter will be device-dependent. Using THROW_CHECK_LE seems more appropriate.

sift.cc

@@ -99,7 +99,7 @@ class Sift {
 #ifdef CUDA_ENABLED
     template <typename dtype>
     sift_output_t ExtractGPU(const pyimage_t<dtype>& image /* [h, w] */) {
-        THROW_CHECK_EQ(options_.max_image_size, sift_gpu->GetMaxDimension());
+        THROW_CHECK_LE(options_.max_image_size, sift_gpu->GetMaxDimension());
         THROW_CHECK(!options_.estimate_affine_shape);
         THROW_CHECK(!options_.domain_size_pooling);