(RE-2222) Push gems to internal server on release

This commit adjusts the ship_gem utility to include a try for pushing
the completed gem to the stickler host, currently rubygems.delivery.puppetlabs.net.
The host name can be overwritten using the environment variable GEM_HOST.
If it fails it puts an error for user to check if they can access the server and have stickler installed.
ASCII art was my idea - however I think I poorly communicated my request. I had something in mind more akin to the warning box hard-coded here: https://github.com/puppetlabs/packaging/blob/master/tasks/00_utils.rake#L1-L20