Changes to adapt to SCE (#59)

Add details to `to_anndata()` docstring (#55)

Make check for empty bframe more robust (#54)

Only populate obsm if spatial coordinates exist (#53)

Change to image handling for consistency (#51)

- Add an affine function that computes a `rasterio.Affine` object given a `scale_factor`. This assumes a simple scaling where the origin is (0,0) in the spatial coordinate system corresponding to the top-left pixel (0,0). More complex alignments would require explicit affine transforms.
- Ensure `img_raster()` consistently returns a PIL.Image.Image.
- Add `to_numpy()` method.
- Changes to how caching works in remote images.

Implement to_anndata() (#50)

Set the expected column names for image data slot (#46)

Implement img_source() (#36)

Load visium as SPE (#16)

* WIP: Implement read_10x_visium

* WIP: Wait for combine ops on SpatialExperiment objs to be implemented

* read_tenx_visium executes successfully

* Initial test for read_tenx_visium passing

* Restrict scipy version to be compatible with python>=3.9

* WIP: Working on last test case for read_tenx_visium

* Fix test_tissue_positions_files test case

* Update CHANGELOG

* Handle paths and urls more reliably

* Localize dependencies

Implement the SFE class (placeholder until there's an official versio…

…n) (#21)