Changing default output folder to _output

.gitignore

@@ -22,4 +22,5 @@ tmp
 *.a
 mkmf.log
 _img
-samples/_img
+samples/_img
+samples/_output/*.png

lib/squib/api/save.rb

@@ -1,13 +1,13 @@
 module Squib
   class Deck
   
-    def save(range: :all, format: :png, prefix: "card_")
+    def save(range: :all, dir: "_output", format: :png, prefix: "card_")
       format = [format].flatten
-      save_png(range: range, prefix: prefix) if format.include? :png
+      save_png(range: range, dir: dir, prefix: prefix) if format.include? :png
       save_pdf if format.include? :pdf
     end
     
-    def save_png(range: :all, dir: "_img", prefix: 'card_')
+    def save_png(range: :all, dir: "_output", prefix: 'card_')
       range = rangeify(range)
       range.each { |i| @cards[i].save_png(i, dir, prefix) }
     end