Piexif

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- Fix failure to decode a minimal 1 x 1 pixel JPEG. Related to https://github.com/hMatoba/Piexif/pull/93.

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- Resolve issue. https://github.com/hMatoba/Piexif/issues/64

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- Ignore XMP segment. Related to https://github.com/hMatoba/Piexif/pull/74.

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- "load", "insert", and "remove" support WebP format.

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- Added helper function to read and write "UserComment".
- Added to support for SignedByte, SigendShort, Float, and Double.

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- Added explicit InvalidImageDataError exception to aid users. Related to https://github.com/hMatoba/Piexif/issues/30.
- Fixed minor issue with tests.
- Removed minor amounts of unused logic.
- Updated .travis.yml for Python and Pillow versions.