Remove package scripts before install

Any `package.json` scripts that would run on `npm install` will be removed while dependencies are being installed. This lets us install parent packages first without the fear of a child package not being ready-to-use in a script.

Why would I want that? Installing dependencies of parents first lets children use `link:` to inherit dev dependencies from their parents. This reduces install times.

The removed scripts are restored after install, and they're executed in topological order (children first).