Add `ant clean` to the script that publishes the docs
Add `ant clean` to the script that publishes the docs

Summary:
- Add `ant clean` to the beginning of the script that publishes the
  documentation to GitHub pages. This command removes any residual files
  in the Buck source tree that could interfere with the process of
  publishing the docs.

Reviewed By: philipjameson

fbshipit-source-id: bc3e186

shs96c/buck,shs96c/buck,JoelMarcey/buck,romanoid/buck,LegNeato/buck,kageiit/buck,SeleniumHQ/buck,rmaz/buck,shs96c/buck,kageiit/buck,romanoid/buck,romanoid/buck,JoelMarcey/buck,LegNeato/buck,romanoid/buck,nguyentruongtho/buck,LegNeato/buck,Addepar/buck,brettwooldridge/buck,facebook/buck,facebook/buck,shs96c/buck,kageiit/buck,romanoid/buck,brettwooldridge/buck,zpao/buck,brettwooldridge/buck,rmaz/buck,LegNeato/buck,JoelMarcey/buck,rmaz/buck,romanoid/buck,brettwooldridge/buck,shs96c/buck,zpao/buck,brettwooldridge/buck,zpao/buck,shs96c/buck,SeleniumHQ/buck,romanoid/buck,romanoid/buck,shs96c/buck,LegNeato/buck,brettwooldridge/buck,JoelMarcey/buck,JoelMarcey/buck,shs96c/buck,brettwooldridge/buck,SeleniumHQ/buck,SeleniumHQ/buck,zpao/buck,LegNeato/buck,Addepar/buck,romanoid/buck,brettwooldridge/buck,brettwooldridge/buck,Addepar/buck,rmaz/buck,JoelMarcey/buck,rmaz/buck,facebook/buck,Addepar/buck,Addepar/buck,rmaz/buck,facebook/buck,SeleniumHQ/buck,LegNeato/buck,facebook/buck,brettwooldridge/buck,rmaz/buck,nguyentruongtho/buck,LegNeato/buck,rmaz/buck,JoelMarcey/buck,LegNeato/buck,SeleniumHQ/buck,JoelMarcey/buck,JoelMarcey/buck,romanoid/buck,rmaz/buck,kageiit/buck,JoelMarcey/buck,nguyentruongtho/buck,rmaz/buck,Addepar/buck,kageiit/buck,rmaz/buck,Addepar/buck,nguyentruongtho/buck,rmaz/buck,romanoid/buck,SeleniumHQ/buck,Addepar/buck,LegNeato/buck,Addepar/buck,JoelMarcey/buck,SeleniumHQ/buck,LegNeato/buck,nguyentruongtho/buck,kageiit/buck,LegNeato/buck,zpao/buck,SeleniumHQ/buck,brettwooldridge/buck,shs96c/buck,rmaz/buck,romanoid/buck,shs96c/buck,nguyentruongtho/buck,facebook/buck,SeleniumHQ/buck,Addepar/buck,zpao/buck,shs96c/buck,SeleniumHQ/buck,JoelMarcey/buck,kageiit/buck,brettwooldridge/buck,JoelMarcey/buck,shs96c/buck,shs96c/buck,LegNeato/buck,brettwooldridge/buck,facebook/buck,nguyentruongtho/buck,zpao/buck,SeleniumHQ/buck,SeleniumHQ/buck,Addepar/buck,Addepar/buck,Addepar/buck,romanoid/buck