Switch to NCC based build

[sheck]

In planningcenter/balto-eslint#18 we switched from tracking node_modules to an ncc based build. I attempted to do the same for this repo this morning but ran into a blocking issue.

The static asset relocator webpack plugin that ncc uses copies create_minimal_gemfile.rb and action.rb into the dist folder. It is missing the rest of the ruby files. Ideally, we don't want to copy the files in the first place.

There currently does not seem to be a way to configure this (ncc lists zero configuration on their readme as a design goal) without manually invoking ncc via node (which does not feel like a great solution at the moment).

If NCC changes (or the static relocator plugin does) or if another way to configure the plugin becomes available, we should look into this again.