upping hydro sync threshold to 750
Merge branch 'master' of github.com:ros-infrastructure/buildfarm
correct usage of empy substitution fixes #153  solves comment in 9f07cc891dcea43b152559f290c5e867b7c4ce30 requiring apt-get update to take arch argument
Merge pull request #156 from ros-infrastructure/fix_163

Fix #153