[COOK-3377] Adds a configurable wait time to runit scripts

Addresses [COOK-3377](http://tickets.opscode.com/browse/COOK-3377). 

This adds a new attribute `runit_wait_time` to the `application_ruby`
provider that allows setting the time runit will wait before timing
out. It defaults to 7, which is runit's default.

It's possible that this should be moved to the runit_service LWRP, but this was the simplest fix at the time, as it only requires 3 lines to address.

Feedback appreciated.