title: NSNumberFormatter doesn't allow typing decimal numbers
body: <p>I am totally bewildered using NSNumberFormatter.  This should be totally simple but I can't get it to work.</p>
  
  <p>I'd like to set an NSTextField to allow typing decimal numbers, either with a decimal point or without.  Here is what I'd think would work:</p>
  
  <pre><code>NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
  [formatter setNumberStyle:NSNumberFormatterDecimalStyle];
  [formatter setMinimumFractionDigits:0];
  [formatter setMaximumFractionDigits:4];
  [formatter setAllowsFloats:YES];
  [[timeFlowMultiplierTF cell] setFormatter:formatter];
  </code></pre>
  
  <p>However, when typing in the textfield, pressing the "period" key for the decimal point doesn't yield one.  Typing "3.14" give me "314".  Throwing in [formatter setAlwaysShowsDecimalSeparator:YES] will initially format the number correctly, but if I type over it, I once again cannot type the decimal point.</p>
  
  <p>What am I missing here?  You would think this would be really simple</p>