added redirecting index.html

see
http://stackoverflow.com/questions/5411538/how-to-redirect-from-an-html-page
and
http://stackoverflow.com/questions/503093/how-can-i-make-a-redirect-page-in-jquery-javascript

Change-Id: If01cd52827b484623778eb193e1893ac8afa468b
Merge pull request #135 from cthiebaud/gh-pages

fix broken link in sap.github.io: added redirecting index.html