Merge pull request #455 from elingg/master

Enhancement 436
Support for new ContainerInfo message in Mesos
Updated Mesos dependency to master snapshot
Merge pull request #439 from mesosphere/dockerinfo

Consistency with upcoming docker support in Mesos
App deletion defaults to force=true.
Default number of app instances = 1
GET /v2/apps/some/app now lists active deployments
Merge pull request #457 from mesosphere/issue-452-list-app-deployments

GET /v2/apps/some/app now lists active deployments
Update Docker.json
Store groups before initiating a deploy.
fix app ids on update
Persist apps before deploying them so that they can show up in the UI
Merge pull request #459 from olix0r/issue-458

Issue 458 -- Store groups & apps before executing updates
Updated docs to reflect current features
Update REST.md
#438 temporary fix for TaskTracker races
fixes #456 - correctly re-add app to TaskQueue when it fails to start in deployment
Fixed duplicate health checks in example JSON
Updated regex that recognizes valid path IDs
Updated REST docs re: app structure