title: pywinauto type_keys() won't send all keys
body: <p>I'm doing some windows automation and I need to import a file into a tool using the 'Open' dialog.  I have this code</p>
  
  <pre><code> w_open_handle = pywinauto.findwindows.find_windows(title=u'Open', class_name='#32770')[0]
   w_open = app.window_(handle=w_open_handle)
  
   # Enter filename in edit box
   w_open['File &amp;name'].type_keys("export.txt")
  </code></pre>
  
  <p>When I run this I notice that only the keys <strong>"rt.txt"</strong> get sent to the <em>File Name</em> edit box on the window. I've tried other names instead of "export.txt" but in every case the first few keys are not sent. I thought perhaps a small delay between opening the dialog and sending the keys would help, but to no avail. </p>
  
  <p>Can anyone tell me what's going on here?</p>
  
  <p><em>Python 3.4.5 (I need this version because of other package dependencies)</em></p>
  
  <p><em>Windows 10</em></p>