Pycaption

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- Always skip doubled special characters, not just in case the cue starters are doubled.

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- Fix an issue with WebVTT writer text positioning on break inside a cue.
- Prevent creating a repositioning command to the same coordinates.

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- Mid-row codes only add spaces only if there isn't one before.
- Mid-row codes add spaces only if they affect the text in the same row (not adding if it follows break or PACS).
- Remove spaces to the end of the lines.
- Close italics on receiving another style setting command.
- Throw an CaptionReadNoCaptions error in case of an empty input file is provided.
- Ignore repositioning commands which are not followed by any text before breaks.
- Mid-row codes will not add the space if it is in front of punctuation.
- Fix a bug with background codes when the InstructionNodeCreator collection is empty.
- Fix a bug WebVTT writer adding double line breaks.

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- Pinned nltk to 3.8.0

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- A space should not be placed before a mid row code if it follows a PAC command or a Tab Offset
- The backspace command should be treated like other commands and duplicates should be skipped if PAC commands are duplicated
- Prevent webvtt writer from creating a new cue in case of line break
- In case of style setting PAC which also breaks the line, we add the break first, then the style tag

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- Yanked.