`screeps-server-mockup` is removed in #113, which relied on `screeps` and in turn on `node-gyp`, which required Python 2.
No other packages depend on Python 2. Since #113 is merged, Python 2 is no longer required for this repository.
This PR updates the repository's readme accordingly.
rollup-plugin-clean doesn't work with the latest rollup, use rollup-plugin-clear instead.
Explicitly set module resolution to be Node.
Specify the tslint project which allows rules based on type info to run.
Update some dependencies to newer versions.
