title: AssertionError: build-tools-23.0.0 doesn't match build-tools-23.0.0-preview
body: <p>I was having trouble with my Android Studio install, it was crashing every time I added a widget to a layout in design view.  So I downloaded the latest version which happened to be a preview build.  This fixed the crashing.  It wasn't an installer though, it was just all of the files zipped.  So I deleted my old Android Studio version and replaced it with this preview version.</p>
  
  <p>Now I'm getting this error every time I open AS:
  <code>AssertionError: build-tools-23.0.0 doesn't match build-tools-23.0.0-preview</code>
  Also, AS no longer recognizes my phone when I try to build my app so I can't test it.  I'm not sure if these two problems are related.</p>