Control node_modules

[lindsayplatt]

Currently, when you install webpack, all node modules are loaded and stored in node_modules/ (there are thousands of files). We are gitignoring that file in this project for now. We want this task to look at two things:

1. figure out if we can choose which node modules to include, and
2. determine if caching these on s3 and having a fetch step to put into node_modules/ will mean people won't have to install everything themselves.