title: Convert numbers to letters beyond the 26 character alphabet
body: <p>I'm creating some client side functions for a mappable spreadsheet export feature.</p>
  
  <p>I'm using jQuery to manage the sort order of the columns, but each column is ordered like an Excel spreadsheet i.e. a b c d e......x y z aa ab ac ad etc etc</p>
  
  <p>How can I generate a number as a letter? Should I define a fixed array of values? Or is there a dynamic way to generate this?</p>