Curver

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* Fixed twist homology action typo.

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* Minimise and shorten now only return encodings.
* Fixed shorten ordering bug.
* Fixed appveyor build process.

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* Generalised intersection code.
* Collated peripheral components code.
* Fixed documentation typos.
* More unittests.

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* New notion of short.
* Removed TrainTracks class, incorporated vertex cycles methods into MultiCurves.
* More performance.
* Simplified hypothesis strategy code.

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* Licence hotfix.

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* Fixed numpy dtype bug.
* Added first version of SLP data structure.
* Switched to MIT licence.
* Using tox-travis.
* Whitespace, formatting, Flake8.