Major health check refactoring.

- Modified protocol buffer backing health checks
- Task health checks are now executed by short-lived, per-request actors
- Upgrades akka and spray library versions
Merge branch 'master' into wip-health-checks-refactored
Removed @Provides method for HealthCheckManager
Add healthCheckResults to the apps task resource
Merge pull request #217 from mattstep/wip-health-checks-refactored

Add healthCheckResults to the apps task resource
Rebase: master
Merge branch 'master' into wip-health-checks-refactored
HealthCheck primitives for new Jackson module
Removed unused message type and method for HC
Added test for TCP HC, fixed HC timeout deser
Concludes merge from master
Updated default values in HealthCheck
Normalized deep equality test
Added inline comment about duration granularity
HTTP Health Check permits 2xx codes by default
Added `firstSuccess` and `alive` health properties
Added healthChecks to AppUpdate deser
Rebase: master
workaround for AppUpdate deserialization
Move wiki page change to REST template

This change was incorrectly made to the generated REST.md in commit
ee4db3a259d6111627ad398f4a20e7c6c9f4843a. This moves the same change
to the template.

Properly fixes #189.