Test against a multi host grid

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Support scheduling jobs based on host attributes

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Support setting environment variables for scheduled jobs

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Support assigning volumes to scheduled jobs

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Support setting explicit exposed ports for scheduled jobs

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Raise an error if no hosts match a filter

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Merge pull request #8 from flynn/schedule-updates

Support setting env vars, volumes and explicit ports for scheduled jobs