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.
I misled you on this because I misread the code. Table-like designs in Bootstrap do not have a trailing line. This `<hr>` should be appended.

Check out http://getbootstrap.com/css/#tables. There is no line under the bottom `<tr>`.