title: Centering buttons dynamically as added with bootstrap
body: <p>I'm using angular bootstrap.  At the top of our page we have a section that will be used for various control dropdowns.  I want to have a 3-4 dropdowns with ng-if on them, having the appear or disappear depending on rather or not a given page allows the functionality of the dropdowns.</p>
  
  <p>I would like these dropdowns to be centered.  I may define btn 1, 2, 3, and 4 in order, but if only btn 3 and btn 4 are active they should show on the middle of the page, not on the right side.  In other words if a dropdowns is disabled due to the ng-if argument the visible dropdowns should center align as if the other's never existed.  Each dropdowns should be a standard width, so that I'm confident that all dropdowns will fit on a single row if all were active.</p>
  
  <p>I'm having a horrible time getting this done, despite feeling that it should be trivially simple behavior.  I've tried pagnation-centered, but it didn't seem to do anything.  I've tried placing them in button groups, but that doesn't seem to be working either.</p>
  
  <p>Can someone point me to the appropriate bootstrap classes to make this work?</p>