title: Ember: incrementProperty interaction with button and input
body: <p>I have a numeric property that can be changed with a button click (using incrementProperty) or through direct input with a text field.</p>
  
  <p>When both are used together, the incrementProperty starts appending "1" to the end of the number instead of incrementing it.</p>
  
  <p>See the problem in this <a href="http://emberjs.jsbin.com/jimafuqa/1/edit?html,js,output" rel="nofollow">simple Ember jsbin</a> I modified.</p>
  
  <p>To reproduce:</p>
  
  <ol>
  <li>Enter a number in the text field.</li>
  <li>Click the <strong>+</strong> button.</li>
  </ol>
  
  <p>Strangely, decrementProperty seems to work fine. If you follow the steps above and then click the <strong>-</strong> button, it seems to reset the value from a string to a number and both increment and decrement work fine. Similarly, if you type in a number and click the <strong>-</strong> button, everything works fine. Is this a bug, or am I missing something?</p>