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* Officially removed Python 2 support.
* Disjoint sum supports a dictionay specifying multiplicities.
* Stripping leading and trailing identity isometries for performance.
* Rewritten to assume that laminations are the correct subclass.
* Switched to left_weight and right_weight.
* Removed Coveralls support.
* More figures for documention.
* Using six.
* MCG now use SLP to parse creation strings.
* Fixed bug where twists could occur even when drop=0.