Allow user and password in Zookeeper URL

This allow us to use a Zookeeper URL like: zk://user1:pass1@host1:123,host2,host3:312/path
Fix docs for `LIKE` constraint
Add `UNLIKE` constraint
don't send answers in MarathonSchedulerActor, when sender is noSender
fixes #648 - TCP health checks don't resolve
Merge pull request #655 from mesosphere/wip-639-deadletters-drexin

fixes #639 - don't send answers in MarathonSchedulerActor, when sender is noSender
Merge pull request #656 from mesosphere/wip-648-resolve-hc-hostnames-drexin

fixes #648 - TCP health checks don't resolve
Fix broken AppDefinition health check validation

- Container.Docker.portMappings is now an Option
- New health check portIndex validation test
- Updated validation error messages
- Fixes #644
Update spray dependency for Scala 2.11

- Fixes class loader errors on launch
- Adds SBT dependency tree plugin
Merge pull request #658 from mesosphere/spray-2.11

Update spray dependency for Scala 2.11
Addressed #657 review comments from @drexin
Fix $HOST env variable for command health checks

- Removed unused Command.toProtoWithEnvironment
- Added env variable checks in TaskBuilderTest
- Added offer.hostname to the env in taskInfo.commandInfo.
Added command health check example JSON.
Merge pull request #645 from iven/docs

Fix docs for `LIKE` constraint and add `UNLIKE` constraint
fixes #663 - Fix scaling of apps with health checks
Merge pull request #665 from mesosphere/662-command-hc-env

Fix $HOST env variable for command health checks
Merge pull request #657 from mesosphere/644-portindex-validation

Fix broken AppDefinition health check validation
Merge pull request #666 from mesosphere/wip-663-fix-scaling-drexin

fixes #663 - Fix scaling of apps with health checks
fixes #669 - Reset rate limiters when app is stopped or changed
Merge pull request #675 from mesosphere/wip-669-reset-rate-limiters-drexin

fixes #669 - Reset rate limiters when app is stopped or changed