Use empty string when no ports to prevent "undefined"

If a task is not assigned any ports, it currently prints the string
"undefined" after the hostname since the portsString var is not
initialized:

    hostnameundefined

Assign portsString a blank string so tasks with no ports print just the
hostname:

    hostname
Conflicts:
	src/main/resources/assets/js/dist/main.js
	src/main/resources/assets/js/dist/main.js.gz
Use PATCH when updating # of instances

Avoid using PUT so the app state does not have to be sent just to change
the number of instances.
Merge pull request #251 from mesosphere/use-patch-for-instances

Use PATCH when updating # of instances