Pypdf3

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- Fix issue with PDF's using /Prev=0 in the xref trailer

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- Optimize Travis CI config
- Add automated PyPi deployment to Travis CI config

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- First distutils-capable true public release. Supports a wide variety of PDF
files that I found sitting around on my system.

- Does not support some PDF 1.5 features, such as object streams,
cross-reference streams.

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- Added tqdm to setup.py install_requires
- Modified progress bar message for pdf.py write method

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- Added progress bar to PdfFileWriter write method

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- Added overwrite_permissions parameter to encrypt module to manually
specify PDF /P value