Russian-tagsets

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- OpenCorpora -> Universal Dependencies conversion support (UD 1.4, UD 2.0,
Dialog 2017 tagset).
- ``convert`` function accepts optional ``word`` argument - conversion rules
may now depend on a word itself, not only on its tag;
- Python 3.2, 3.3 and 2.6 support is dropped;
- packaging improvements.

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- Handle "abbr" grammeme in OpenCorpora -> RusCorpora conversion.

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- Added support for Init OpenCorpora grammeme.

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- Added support for initials in OpenCorpora -> RusCorpora conversion rules;
- small code cleanup.

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- Improved OpenCorpora -> RusCorpora rules;
- Anph grammeme is added to OpenCorpora rules.

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- Improved OpenCorpora -> RusCorpora rules.