return absolute URLs
Increase session lifetime to 3 days

3600 * 24 * 3 = 259200
Add comment for lifetime default
adjust render tests
only load visible ads
Merge pull request #1424 from dlondero/issue-1424

Increase session lifetime
Merge pull request #1423 from christopheschwyzer/issue-1423

use absolute URLs
Merge pull request #1427 from christopheschwyzer/issue-1427

Only load visible openx advertisements
Merge branch 'master' of github.com:cargomedia/CM into issue-1132
use instanceof