Enhance object interface to allow closure per main suite

Now, when a function is passed to the object interface, it will
be executed once for each environment, which ensures that a clean
closure is created for each environment when running functional
tests in the test runner.
Add code coverage to runner code
Update Istanbul to latest
Exit process with correct exit code if Sauce tunnel fails
Merge branch 'master' into geezer

Conflicts:
	lib/interfaces/object.js
	lib/reporters/runner.js