Add information about nodejs dependency.

Closes #26

README.md

@@ -7,15 +7,17 @@ Keeps track of membership to a society.
 ### Prerequisites
 
 * Ruby (See `.ruby-version` for the version you have to install)
+* Nodejs (for building assets, not required for production)
 * Postgres
 
 ### Set-up
 
 Clone this repository and run the following from the working directory:
 
     bin/setup
+    yarn install
 
-This will install dependencies and create a development and test database.
+This will install dependencies, create a development and test database, and install nodejs dependencies.
 
 ### Start
 
@@ -25,6 +27,9 @@ To start a local server, run:
 
 By default, this will start a local webserver on [http://localhost:3000](http://localhost:3000)
 
+And
+
+    yarn build --watch
 
 ## Testing
 
@@ -42,8 +47,8 @@ Voting can be enabled by setting a `VOTE_URL_TEMPLATE` environment variable.
 
 When set, a message will appear on the home page, and members will be able to get a unique link emailed to them through a form, which substitutes `%token%` in the URL template with each member's unique `voting_token`.
 
-## Maintenance
+## Deployment
 
-### Upgrading Rails
+To deploy this app you need Nodejs to compile the assets, but only Ruby to run the production server.
 
-Follow the [Upgrading Rails Guide](https://guides.rubyonrails.org/upgrading_ruby_on_rails.html) which, as of May 10, 2020 suggests updating each Rails version incrementally and running `bin/rails app:update` to compare new defaults.
+Heroku should identify you need those two dependencies, if it does not, please refer to the [Buildpacks](https://devcenter.heroku.com/articles/buildpacks) documentation.