Add quantity explosion to xlsx and csv

Closes #78

samples/csv_import.rb

@@ -15,4 +15,12 @@ Squib::Deck.new(cards: 2) do
 end
 
 # CSV is also a Squib-module-level function, so this also works:
-data = Squib.csv file: 'sample.csv'
+data      = Squib.csv file: 'quantity_explosion.csv' # 2 rows...
+num_cards = data['Name'].size                        #          ...but 4 cards!
+
+Squib::Deck.new(cards: num_cards) do
+  background color: :white
+  rect # card border
+  text str: data['Name'], font: 'Arial 54'
+  save_sheet  prefix: 'sample_csv_qty_', columns: 4
+end

samples/excel.rb

@@ -14,6 +14,18 @@ Squib::Deck.new(cards: 3) do
   save format: :png, prefix: 'sample_excel_' #save to individual pngs
 end
 
+# xlsx is also a Squib-module-level function, so this also works:
+data      = Squib.xlsx file: 'explode_quantities.xlsx' # 2 rows...
+num_cards = data['Name'].size                          #          ...but 4 cards!
+
+Squib::Deck.new(cards: num_cards) do
+  background color: :white
+  rect # card border
+  text str: data['Name'], font: 'Arial 54'
+  save_sheet  prefix: 'sample_xlsx_qty_', columns: 4
+end
+
+
 # Here's another example, a bit more realistic. Here's what's going on:
 #   * We call xlsx from Squib directly - BEFORE Squib::Deck creation. This
 #     allows us to infer the number of cards based on the size of the "Name"

samples/quantity_explosion.csv

@@ -0,0 +1,3 @@
+Name,Qty
+Basilisk,3
+High Templar,1