Changed VtkElement to not inherit from object.
Changed VtkElement to not inherit from object.

Changed
-------
* VtkElement no longer inherits from builtins.object. This was needed
  because in Python 2.7 xml.dom.minidom.Element was not a new-style
  class. However, in Python 3.x it is, which causes a MRO error. Removed
  object from VtkElement since super is no longer used so it should be
  OK.

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