New Features:
- Encoding for `webp` is now available with the native library. This needs to
  be activate explicitly with the `web-encoder` feature.
- `exr` decoding has gained basic limit support.

Bug fixes:
- The `Iterator::size_hint` implementation of pixel iterators has been fixed to
  return the current length indicated by its `ExactSizeIterator` hint.
- Typos and bad references in the documentation have been removed.

Performance:
- `ImageBuffer::get_pixel{,_mut}` is now marked inline.
- `resize` now short-circuits when image dimensions are unchanged.