title: Trying to center align button in td
body: <p>I'm having trouble centering a button in a td.</p>
  
  <p>This is probably a simple CSS issue, but the app is using bootstrap, AngularJS, AngularJS-ui-bootstrap, and ngTable.  I've included all of these components in my <a href="http://plnkr.co/edit/ks6xTfJxXEQnmVmtJd3M">plunkr</a>.</p>
  
  <p>I'm trying to set "horizontal-align: middle" on the td with the button, but that doesn't seem to get applied.  The button still leans to the left side of the cell.</p>