Provide a CLI tool to sign your scripts

[kurtisnelson]

Right now you have to go to playground and send to gist to get your script signed. Ideally we should have a CLI in here that you pass the script name and your keys to and it signs it in place in the sourcetree.

[kurtisnelson]

Now that we've got a toolchain for creating scripts and such, we can do this.

What keys does the developer need to do the signing?