Tons of documentation work

lib/squib/api/data.rb

@@ -3,10 +3,18 @@ require 'roo'
 module Squib
   class Deck
 
+    #@api private todo
     def csv(file: 'deck.csv', header: true)
       raise 'Not implemented!'
     end
 
+    # Convenience method for pulling Excel data from `.xlsx` files
+    #   Pulls the data into a Hash of arrays based on the columns. First row is assumed to be the header row. 
+    #   See the example at {file:samples/excel.rb samples/excel.rb}. The accompanying Excel file is in the [source repository](https://github.com/andymeneely/squib/tree/master/samples)
+    #
+    # @param file: [String] the file to open. Must end in `.xlsx`. Opens relative to the current directory.
+    # @param sheet: [Integer] The zero-based index of the sheet from which to read.
+    # @api public
     def xlsx(file: 'deck.xlsx', sheet: 0)
       s = Roo::Excelx.new(file)
       s.default_sheet = s.sheets[sheet]