Polylx

* Added MAEE (minimum area enclosing ellipse) to grain shape methods
* Removed embedded IPython and IPython requirements

* IPython added to requirements

* Sample has pairs property(dictionary) to map boundary id to grains id
* Sample triplets method returns list of grains id creating triple points

* Examples added to distribution

* Sample neighbors_dist method to calculate neighbors distances
* Grains and Boundaries nndist to calculate nearest neighbors distances
* Fancy indexing with slices fixed
* Affine transformations affine_transform, rotate, scale, skew, translate
methods implemented for Grains and Boundaries
* Sample name atribute added
* Sample bids method to get boundary id's related to grain added

* PolyShape name forced to be string
* Creation of boundaries is Grains method