Add start_time and end_time to builds
Add restart management command
Add Build.has_timed_out
Add setting of start_time and end_time on Build
Add test for Build.has_timed_out()
Merge branch 'master' of github.com:frigg/frigg into issue95-handle-timeout

Conflicts:
	frigg/builds/models.py
	frigg/builds/test_models.py
Merge pull request #122 from frigg/issue95-handle-timeout

Fix #95, Add handling of builds that seems to have timed out