[site] Updated downloads-page for 0.26.0.
[site] Updated downloads-page for 0.26.0.

Review: https://reviews.apache.org/r/41485/

asamerh4/mesos,Aman-Jain-14/customizedMesos,andschwa/mesos,jpeach/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,andschwa/mesos,asamerh4/mesos,gsantovena/mesos,kaysoky/mesos,jpeach/mesos,zmalik/mesos,neilconway/mesos,neilconway/mesos,andschwa/mesos,dforsyth/mesos,dforsyth/mesos,reneploetz/mesos,craimbert/mesos,craimbert/mesos,craimbert/mesos,zmalik/mesos,abudnik/mesos,Gilbert88/mesos,asamerh4/mesos,neilconway/mesos,kaysoky/mesos,chhsia0/mesos,kaysoky/mesos,zmalik/mesos,asamerh4/mesos,craimbert/mesos,Gilbert88/mesos,reneploetz/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,yuquanshan/customizedMesos,chhsia0/mesos,neilconway/mesos,reneploetz/mesos,abudnik/mesos,jpeach/mesos,asamerh4/mesos,andschwa/mesos,dforsyth/mesos,verizonlabs/mesos,chhsia0/mesos,kaysoky/mesos,dforsyth/mesos,neilconway/mesos,dforsyth/mesos,kaysoky/mesos,yuquanshan/customizedMesos,craimbert/mesos,craimbert/mesos,zmalik/mesos,asamerh4/mesos,Gilbert88/mesos,jpeach/mesos,gsantovena/mesos,craimbert/mesos,abudnik/mesos,reneploetz/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,chhsia0/mesos,neilconway/mesos,yuquanshan/customizedMesos,neilconway/mesos,Aman-Jain-14/customizedMesos,kaysoky/mesos,verizonlabs/mesos,abudnik/mesos,zmalik/mesos,jpeach/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,yuquanshan/customizedMesos,chhsia0/mesos,dforsyth/mesos,dforsyth/mesos,andschwa/mesos,asamerh4/mesos,jpeach/mesos,abudnik/mesos,abudnik/mesos,gsantovena/mesos,Gilbert88/mesos,andschwa/mesos,Gilbert88/mesos,kaysoky/mesos,abudnik/mesos,zmalik/mesos,gsantovena/mesos,Gilbert88/mesos,verizonlabs/mesos,gsantovena/mesos,reneploetz/mesos,chhsia0/mesos,verizonlabs/mesos,reneploetz/mesos,andschwa/mesos,jpeach/mesos,verizonlabs/mesos,verizonlabs/mesos