Tweak gh-pages-update.sh
Tweak gh-pages-update.sh

This script generates a new gh-pages index.html and copies javadocs
for the release to /javadoc/$VERSION/ and /javadoc/current/.  This
commit makes its detection of whether the gh-pages branch already
exists more robust by using a git plumbing command instead of checking
file existence in the .git directory.  Also fix outdated wording
talking about wikidoc in one of the messages it prints to console.

hortonworks/titan,fengshao0907/titan,kalatestimine/titan,qiuqiyuan/titan,anuragkh/titan,anuragkh/titan,jankotek/titan,elkingtonmcb/titan,xlcupid/titan,kangkot/titan,jamestyack/titan,kangkot/titan,ThiagoGarciaAlves/titan,jankotek/titan,ThiagoGarciaAlves/titan,kangkot/titan,kangkot/titan,tomersagi/titan,tomersagi/titan,xlcupid/titan,fengshao0907/titan,elkingtonmcb/titan,anuragkh/titan,wangbf/titan,anuragkh/titan,mwpnava/titan,qiuqiyuan/titan,elkingtonmcb/titan,fengshao0907/titan,tomersagi/titan,mwpnava/titan,jankotek/titan,wangbf/titan,wangbf/titan,nvoron23/titan,mwpnava/titan,mwpnava/titan,ThiagoGarciaAlves/titan,hortonworks/titan,nvoron23/titan,evanv/titan,jamestyack/titan,kalatestimine/titan,nvoron23/titan,fengshao0907/titan,xlcupid/titan,anuragkh/titan,wangbf/titan,hortonworks/titan,kalatestimine/titan,tomersagi/titan,kalatestimine/titan,evanv/titan,kangkot/titan,tomersagi/titan,mwpnava/titan,fengshao0907/titan,evanv/titan,jankotek/titan,ThiagoGarciaAlves/titan,xlcupid/titan,qiuqiyuan/titan,jamestyack/titan,evanv/titan,ThiagoGarciaAlves/titan,evanv/titan,qiuqiyuan/titan,xlcupid/titan,jankotek/titan,wangbf/titan,hortonworks/titan,elkingtonmcb/titan,elkingtonmcb/titan,nvoron23/titan,hortonworks/titan,jamestyack/titan,jamestyack/titan,kalatestimine/titan,qiuqiyuan/titan