sapling.rb: Rubocop and refactor updates

- Fix several rubocop violations
- Update functionality to account for gardner refactor

lib/sapling.rb

@@ -8,19 +8,20 @@ Dir[File.join(__dir__, 'sapling', '*.rb')].each { |file| require file }
 # The main Sapling interface.
 class Sapling < Thor
   desc 'read TREE', 'Load and traverse the TREE'
-  def read(tree)
-    exit unless verify_tree(tree)
+  def read(file)
     puts 'Welcome to Sapling, a Dialogue Tree Utility.'
-    speaker = Dialogue::Speaker.new(YAML.load_file(tree), false)
+    exit unless verify_tree(file)
+    tree = Gardner::Plot.new(YAML.load_file(file), false)
+    speaker = Dialogue::Speaker.new(tree)
     speaker.conversation
   end
 
   desc 'edit TREE', 'Edit a new or existing TREE'
-  def edit(tree = '')
+  def edit(file = '')
     puts 'Welcome to Sapling, a Dialogue Tree Utility.'
     if !tree.empty?
-      puts "Loading tree: #{tree}"
-      exit unless verify_tree(tree)
+      puts "Loading tree: #{file}"
+      exit unless verify_tree(file)
       gardner = Planter::Spade.new(YAML.load_file(tree, false))
     else
       puts 'Creating a new tree!'