Location quantization in 1 km gridding

[deeplycloudy]

Gridding the included test dataset as in the plot_glm_test_data.ipynb example but at 1 km results in a non-contiguous image as shown below. The scale_factor for the x and y coordinate data is 56 micro radians, as noted in glmtools.io.imagery.get_goes_imager_fixedgrid_coords, so that is one place to start. However, the raw flash extent density grid (without using the coordinate data) looks the same as below, so that points to a deeper problem.

[deeplycloudy]

The docs in io.imagery also note that the imagery output format isn't really tested for anything other than 2 km.