Feature: Health checks

@ssorallen Would you take a look at the taskDetailsComponent update?

I updated this page https://github.com/mesosphere/marathon/wiki/Test-App-Commands to contain the toggle server i build to be able to toggle the health of the end point of the health check.
This makes the breadcrumbs blend too much:

![screenshot 2014-06-10 10 21 21](https://cloud.githubusercontent.com/assets/29612/3233972/c0880482-f0c3-11e3-8593-fb84391b61da.png)

A muted `#333` gives them enough differentiation from other content:

![screenshot 2014-06-10 10 21 13](https://cloud.githubusercontent.com/assets/29612/3233978/cfab6d28-f0c3-11e3-8e32-0a7dbb638f94.png)