README.md in logster-2.3.0 vs README.md in logster-2.3.1

@@ -56,10 +56,14 @@
 If you are seeing the error `No such middleware to insert before: ActionDispatch::DebugExceptions` after installing logster,
 then you are using a conflicting gem like `better_errors` or `web-console`.
 
 To avoid this error, make sure logster is added behind those conflicting gems in your Gemfile.
 
+If you're using Logster with a non-rails app, you'll need to be careful that the env hashes of messages that Logster receives don't contain strings with invalid encoding because at some point Logster calls `#to_json` on the message env and the method will fail with `JSON::GeneratorError`.
+
+The reason this doesn't happen in rails apps is because ActiveSupport has a monkey patch for [`#to_json`](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/object/json.rb).
+
 ### Mount using warden (devise)
 ```
   admin_constraint = lambda do |request|
     request.env['warden'].authenticate? and request.env['warden'].user.admin?
   end
@@ -90,10 +94,10 @@
 ## Contributing
 
 1. Fork it ( https://github.com/discourse/logster/fork )
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Run `cd client-app && npm install`
-4. Run `rake client_dev` to start Sinatra server (port 9292) and Ember server (port 4200). Use Ember server for hot reload for client code.
+4. Run `bundle exec rake client_dev` to start Sinatra server (port 9292) and Ember server (port 4200). Use Ember server for hot reload for client code.
 5. Once you're done making changes, run `./build_client_app.sh` to make and copy a production build to the assets folder.
 6. Commit your changes (`git commit -am 'Add some feature'`)
 7. Push to the branch (`git push origin my-new-feature`)
 8. Create a new Pull Request