Add a javascript contracts package

[joshuahannan]

Issue To Be Solved

We want to be able to release packages in other language so that apps written in those languages can import them to get the contract code defined in the repo, similar to how it is done in Go.

Suggest A Solution

• Design and write a package in lib/javascript/ for getting contract code.
• Use the code in contracts/ and replace the addresses and names with arguments that the caller provides.
• Write tests to make sure the templates are created correctly.