fix rake file

Rakefile

@@ -23,7 +23,7 @@ end
 # Helper Functions
 ###############################################################################
 
-$ensure_dir_exists = ->(dir) { if !Dir.exists?(dir) then Dir.mkdir(dir) end }
+$ensure_dir_exists = ->(dir) { if !Dir.exist?(dir) then Dir.mkdir(dir) end }
 
 def prompt_user_for_confirmation message
   response = nil
@@ -105,7 +105,7 @@ task :generate_derivatives, [:thumbs_size, :small_size, :density, :missing, :im_
     if !file_type
       access_filename=File.join([objects_dir, "#{base_filename}#{extname}"])
       puts "Skipping conversion of file with unsupported extension: #{extname}."
-      if args.missing == 'false' or !File.exists?(access_filename)
+      if args.missing == 'false' or !File.exist?(access_filename)
         puts "Copying #{filename} to objects dir for access as #{access_filename}."
         system("cp #{filename} #{access_filename}")
       end
@@ -122,7 +122,7 @@ task :generate_derivatives, [:thumbs_size, :small_size, :density, :missing, :im_
     # Generate or copy the access image.
     if extname == ".tif" || extname == ".tiff"
       access_filename=File.join([objects_dir, "#{base_filename}.jpg"])
-      if args.missing == 'false' or !File.exists?(access_filename)
+      if args.missing == 'false' or !File.exist?(access_filename)
         puts "Creating #{access_filename}"
         system("#{cmd_prefix} -flatten #{access_filename}")
       else
@@ -131,7 +131,7 @@ task :generate_derivatives, [:thumbs_size, :small_size, :density, :missing, :im_
     elsif extname == ".pdf"
       access_imagefilename=File.join([objects_dir, "#{base_filename}.jpg"])
       access_filename=File.join([objects_dir, "#{base_filename}#{extname}"])
-      if args.missing == 'false' or !File.exists?(access_filename)
+      if args.missing == 'false' or !File.exist?(access_filename)
         puts "Creating #{access_imagefilename}"
         system("#{cmd_prefix} -flatten #{access_imagefilename}")
         puts "Copying #{filename} to objects dir for access as #{access_filename}."
@@ -141,7 +141,7 @@ task :generate_derivatives, [:thumbs_size, :small_size, :density, :missing, :im_
       end      
     else
       access_filename=File.join([objects_dir, "#{base_filename}#{extname}"])
-      if args.missing == 'false' or !File.exists?(access_filename)
+      if args.missing == 'false' or !File.exist?(access_filename)
         puts "Copying #{filename} to objects dir for access as #{access_filename}."
         system("cp #{filename} #{access_filename}")
       else
@@ -151,14 +151,14 @@ task :generate_derivatives, [:thumbs_size, :small_size, :density, :missing, :im_
 
     # Generate the thumb image.
     thumb_filename=File.join([thumb_image_dir, "#{base_filename}_th.jpg"])
-    if args.missing == 'false' or !File.exists?(thumb_filename)
+    if args.missing == 'false' or !File.exist?(thumb_filename)
       puts "Creating: #{thumb_filename}";
       system("#{cmd_prefix} -resize #{args.thumbs_size} -flatten #{thumb_filename}")
     end
 
     # Generate the small image.
     small_filename = File.join([small_image_dir, "#{base_filename}_sm.jpg"])
-    if args.missing == 'false' or !File.exists?(small_filename)
+    if args.missing == 'false' or !File.exist?(small_filename)
       puts "Creating: #{small_filename}";
       system("#{cmd_prefix} -resize #{args.small_size} -flatten #{small_filename}")
     end
@@ -206,13 +206,13 @@ task :new_post do
   end
 
   # check dir
-  if !Dir.exists?(post_dir) 
+  if !Dir.exist?(post_dir) 
     puts "Creating #{post_dir}."
     Dir.mkdir(post_dir) 
   end
 
   # make sure file doesn't exist
-  if File.exists?(output_name)
+  if File.exist?(output_name)
     puts "The file #{output_name} already exists! New post not created."
   else
     # write file