makes mayavi an optional dep (not all need 3d)
makes mayavi an optional dep (not all need 3d)

jabooth/menpo-archive,jabooth/menpo-archive,menpo/menpo,yuxiang-zhou/menpo,menpo/menpo,yuxiang-zhou/menpo,patricksnape/menpo,mozata/menpo,jabooth/menpo-archive,mozata/menpo,grigorisg9gr/menpo,jabooth/menpo-archive,mozata/menpo,patricksnape/menpo,menpo/menpo,patricksnape/menpo,yuxiang-zhou/menpo,mozata/menpo,grigorisg9gr/menpo,grigorisg9gr/menpo