Need to build *.js.flow definition files for build files

Using `flow gen-flow-files`, we should have `.js.flow` definition files for `index`, `module/*.js`, `module/sagas/*.js`.

Blockers to this:
- Need to type our `reselect` types properly https://github.com/contactually/redux-capacitor/issues/22
- Need to update to Immutable v4 for the FlowType updates https://github.com/contactually/redux-capacitor/issues/20

Start with the `flow gen-flow-files` command and the `index`, `module/*.js`, and `module/sagas/*.js` paths named in the issue. Review blockers in issues #22 and #20 first; done means the requested `.js.flow` definition files exist for those build files.

Written by the indexing model from the issue text.