Mandatory type annotations for public methods.

- Fixed resulting errors across the codebase.
Merge pull request #696 from mesosphere/style-public-methods-have-type

Mandatory type annotations for public methods.
Enforce line length limit of 120 columns.
    
- Fixed resulting errors across the codebase.
mention --task_launch_timeout for Docker 

Closes #698.
Merge pull request #700 from rasputnik/patch-1

mention --task_launch_timeout for Docker
Merge pull request #699 from mesosphere/style-line-length

Enforce line length limit of 120 columns.
Scheduler launches only current apps.

- Prevents Marathon from launching stale (non-current)
  tasks that have been in the task queue since before
  the latest app update.
Swapped semantics of TaskQueue filter/filterNot

- Behavior now matches the Scala standard library
- Adds tests for filter/filterNot
Renamed TaskQueue.filter => retain, removed filterNot
Merge pull request #702 from mesosphere/launch-only-current-tasks

Scheduler launches only current apps.
Metrics for concrete subtypes of EntityRepository.

- Added a StateMetrics trait.
- Instrumented read/write ops in TaskTracker,
  AppRepository, DeploymentRepository,
  GroupRepository.
- Metrics are available at the /metrics endpoint.
Merge pull request #705 from mesosphere/state-metrics

Metrics for concrete subtypes of EntityRepository.