[Sass] Get rid of an unneeded method on Tree::Node.

lib/sass/engine.rb

@@ -446,7 +446,7 @@ SHORT
     end
 
     def parse_else(parent, line, text)
-      previous = parent.last
+      previous = parent.children.last
       raise SyntaxError.new("@else must come after @if.") unless previous.is_a?(Tree::IfNode)
 
       if text

lib/sass/plugin.rb

@@ -155,6 +155,7 @@ module Sass
     end
 
     def dependencies(filename)
+      Files.tree_for(filename, options)
       # TODO: This won't work in all cases for SCSS.
       # We should store this info in the cache
       # and then re-parse to get it if it's not there.

lib/sass/tree/node.rb

@@ -80,15 +80,6 @@ module Sass
         @children << child
       end
 
-      # Return the last child node.
-      #
-      # We need this because {Tree::Node} duck types as an Array for {Sass::Engine}.
-      #
-      # @return [Tree::Node] The last child node
-      def last
-        children.last
-      end
-
       # Compares this node and another object (only other {Tree::Node}s will be equal).
       # This does a structural comparison;
       # if the contents of the nodes and all the child nodes are equivalent,