Now works through "create_dendextend_options" (Thanks to suggestions by Kurt Hornik and Uwe Ligges).
renamed:
      * cut_lower_fun -> dendextendRcpp_cut_lower_fun
      * get_branches_heights -> dendextendRcpp_get_branches_heights
      * heights_per_k.dendrogram -> dendextendRcpp_heights_per_k.dendrogram
Force  dendextend (>= 0.14.0)
Added dendextendRcpp_ to function names (updated docs)
added remove_dendextendRcpp_options alias (resolves warning)
Added quick "check" command
A TODO reminder for the future:  Check if we have any old_ that should be changed into dendextend_