'Cell' object has no attribute 'diameter' #160
Description
In pyurmde.py, line 1089, the diameter method from the dolfin.Cell class has been removed from the last version of Fenics (see https://fenicsproject.org/olddocs/dolfin/2016.2.0/python/programmers-reference/cpp/mesh/Cell.html#dolfin.cpp.mesh.Cell).
circumradius could be used as a replacement.