title: Updating Optionsmenu issue
body: <p>I have following code and need it to update the same dropdownlist with new values. Currently it just creates a new list to the right of the existing one. Any suggestions on how to achieve this?</p>
  
  <pre><code>import os
  import sys
  import Tkinter as tk
  
  def edit():
  var.set('Choose build')
  choices =['one','two','three','four','five','six','seven','eight','nine','ten']
  
  option = tk.OptionMenu(root, var, *choices)
  option.pack(side='left', padx=10, pady=20)
  
  root.mainloop()
  
  root = tk.Tk()
  var = tk.StringVar(root)
  var.set('Choose build')
  option = tk.OptionMenu(root, var, '')
  
  root.geometry("%dx%d+%d+%d" % (500, 150, 200, 150))
  root.title("QCT Multimedia Build Metrics")
  
  button = tk.Button(root, text="Edit Config", command=edit)
  button.pack(side='left', padx=20, pady=10)
  
  choices = ['one','two','three','four','five']
  
  option = tk.OptionMenu(root, var, *choices)
  option.pack(side='left', padx=10, pady=20)
  
  root.mainloop()
  </code></pre>