Educating typescript re use of `lib` in test imports

[BurtHarris]

With PR #123 (TypeScript Beginnings) is applied and used, there's a strange and undesirable artifact in the built directory: not only does it contain the expected src and test subdirectories, but lib shows up there as well. This is a result of TypeScript processing the babel output in the root level lib directory.

Found a small change in tsconfig.json to avoid this.