updates to vagrant
dump Gemfile + add plugin checks to Vagrantfile
use availableResources, not offer resources
update migrations.sql to be in line with singularity.sql
Merge branch 'master' of github.com:HubSpot/Singularity
doc updates
use String instead of Optional<String>
deploys now delete obsolete future scheduled tasks
Add a different message if we have to kill-9 task
Update vagrant.md
Changes to scheduled & oneoff requests

- Deploys will never kill an ongoing scheduled task
- Once a task finishes, the new deploy’s pending request will cause it
to be scheduled
- Allow N one-offs to run at once
Merge branch 'master' into 0.19.1