Add the ASF events link to the website.
Add the ASF events link to the website.

Update the Mesos website the ASF current event banner described
in http://apache.org/events/README.txt. This is a dynamic banner
that will be updated automatically without the need to update the
website every time for every new event.

Review: https://reviews.apache.org/r/66901/

reneploetz/mesos,abudnik/mesos,reneploetz/mesos,jpeach/mesos,Gilbert88/mesos,jpeach/mesos,reneploetz/mesos,chhsia0/mesos,gsantovena/mesos,jpeach/mesos,abudnik/mesos,Gilbert88/mesos,reneploetz/mesos,andschwa/mesos,chhsia0/mesos,andschwa/mesos,jpeach/mesos,Gilbert88/mesos,chhsia0/mesos,chhsia0/mesos,dforsyth/mesos,dforsyth/mesos,gsantovena/mesos,jpeach/mesos,gsantovena/mesos,abudnik/mesos,Gilbert88/mesos,kaysoky/mesos,dforsyth/mesos,chhsia0/mesos,chhsia0/mesos,kaysoky/mesos,gsantovena/mesos,reneploetz/mesos,andschwa/mesos,kaysoky/mesos,andschwa/mesos,reneploetz/mesos,kaysoky/mesos,abudnik/mesos,gsantovena/mesos,andschwa/mesos,dforsyth/mesos,dforsyth/mesos,abudnik/mesos,jpeach/mesos,dforsyth/mesos,andschwa/mesos,kaysoky/mesos,gsantovena/mesos,dforsyth/mesos,abudnik/mesos,Gilbert88/mesos,abudnik/mesos,chhsia0/mesos,kaysoky/mesos,andschwa/mesos,Gilbert88/mesos,jpeach/mesos,kaysoky/mesos,reneploetz/mesos,gsantovena/mesos,Gilbert88/mesos