use an Array for wrapped help instead of fighting with StringIO

lib/image_optim/runner/option_parser.rb

@@ -43,32 +43,35 @@ def help
         # don't try to wrap if there is too little space for description
         return text if wrapped_width < 20
 
-        wrapped = StringIO.new('')
+        wrapped_text(text, wrapped_width, wrapped_indent, columns)
+      end
+
+    private
+
+      def terminal_columns
+        stty_columns = `stty size 2> /dev/null`[/^\d+ (\d+)$/, 1]
+        stty_columns ? stty_columns.to_i : `tput cols`.to_i
+      end
+
+      def wrapped_text(text, wrapped_width, wrapped_indent, columns)
+        wrapped = []
         text.split("\n").each do |line|
           if line.length <= columns
-            wrapped.puts line
+            wrapped << line << "\n"
           else
-            wrapped.puts line.slice!(wrap_regex(columns)).rstrip
+            wrapped << line.slice!(wrap_regex(columns)).rstrip << "\n"
             if line =~ /^\s/
               line.scan(wrap_regex(wrapped_width)) do |part|
-                wrapped << wrapped_indent
-                wrapped.puts part.rstrip
+                wrapped << wrapped_indent << part.rstrip << "\n"
               end
             else
               line.scan(wrap_regex(columns)) do |part|
-                wrapped.puts part.rstrip
+                wrapped << part.rstrip << "\n"
               end
             end
           end
         end
-        wrapped.string
-      end
-
-    private
-
-      def terminal_columns
-        stty_columns = `stty size 2> /dev/null`[/^\d+ (\d+)$/, 1]
-        stty_columns ? stty_columns.to_i : `tput cols`.to_i
+        wrapped.join(nil)
       end
 
       def wrap_regex(width)