* Changed max gradient functions to return node ID of max gradient.
* Changed max gradient functions to return node ID of max gradient.

== Changed ==

* Functions that calculate the maximum gradient to adjacent cells now
  optionally return the node ID of the cell toward which the gradient is
  greatest. This is controlled by the *return_node* keyword.
  


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