data: fix wrap_n_pad bug

This doesn't make modifications to the original string. If only Ruby used their own convention and did str#concat! instead of str#concat

Fixes #191

[skip ci]

lib/squib/import/data_frame.rb

@@ -86,13 +86,13 @@ module Squib
     end
 
     def wrap_n_pad(str, max_col)
-      str.to_s.
-          concat(' '). # handle nil & empty strings
-          scan(/.{1,34}/).
+      new_str = str.to_s + ' ' # handle nil & empty strings
+      new_str = new_str.
+                  scan(/.{1,34}/). # break down
                   map { |s| (' ' * max_col) + " | " + s.ljust(34) }.
                   join(" |\n").
-          lstrip.      # initially no whitespace next to key
-          concat(" |\n")
+                  lstrip      # initially no whitespace next to key
+      return new_str + " |\n"
     end
 
     def def_column(col)

spec/import/data_frame_spec.rb

@@ -246,6 +246,14 @@ Fun with UTF8! | 👊                                  |
                ╰------------------------------------╯
 EOS
     end
+
+    it 'does not pad the data' do
+      data = Squib::DataFrame.new
+      data['a'] = ['b', 'c']
+      expect(data.to_pretty_text.size).to be > 0
+      expect(data.columns).to eq ['a']
+      expect(data['a']).to eq ['b', 'c']
+    end
   end
 
 end