Changed methods to be staticmethod.
Changed methods to be staticmethod.

Changed
=======

* The following methods are now decorated as staticmethod:
  - def setup_node_cell_connectivity
  - def create_links_from_triangulation
  - def is_valid_voronoi_ridge
  - def create_links_and_faces_from_voronoi_diagram
  These methods don't act on a ModelGrid so should be staticmethods. This
  eliminates the need to create "empty" grids just to use the methods.



cmshobe/landlab,Carralex/landlab,decvalts/landlab,landlab/landlab,SiccarPoint/landlab,SiccarPoint/landlab,ManuSchmi88/landlab,landlab/landlab,laijingtao/landlab,Carralex/landlab,decvalts/landlab,RondaStrauch/landlab,RondaStrauch/landlab,Carralex/landlab,csherwood-usgs/landlab,laijingtao/landlab,landlab/landlab,ManuSchmi88/landlab,ManuSchmi88/landlab,amandersillinois/landlab,csherwood-usgs/landlab,RondaStrauch/landlab,amandersillinois/landlab,cmshobe/landlab,cmshobe/landlab