Assets not compiling

This is driving me crazy - changes to css on my rails site only update when I run rake assets:precompile.

Does anyone know how to fix this, so assets will get compiled as they are changed?

I have a hunch the issue is in this config/environments/development.rb file:

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.
  config.assets.compile = true
  # In the development environment your application's code is reloaded on
  # every request. This slows down response time but is perfect for development
  # since you don't have to restart the web server when you make code changes.
  config.cache_classes = false

  # Do not eager load code on boot.
  config.eager_load = false

  # Show full error reports and disable caching.
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = false

  # Care if the mailer can't send.
  config.action_mailer.raise_delivery_errors = true

  # Print deprecation notices to the Rails logger.
  config.active_support.deprecation        = :log
  config.action_mailer.delivery_method     = :smtp
  config.action_mailer.perform_deliveries  = true
  config.action_mailer.default_url_options = { :host => "http://localhost:3000/" }
  # SMTP settings for gmail
  config.action_mailer.smtp_settings = {
    address:              'smtp.gmail.com',
    port:                 587,
    domain:               'gmail.com',
    user_name:            ENV['gmail_username'],
    password:             ENV['gmail_password'],
    authentication:       'plain',
    enable_starttls_auto: true
  }

  # Raise an error on page load if there are pending migrations.
  config.active_record.migration_error = :page_load

  # Debug mode disables concatenation and preprocessing of assets.
  # This option may cause significant delays in view rendering with a large
  # number of complex assets.
  config.assets.debug = true

  # Asset digests allow you to set far-future HTTP expiration dates on all assets,
  # yet still be able to expire them through the digest params.
  config.assets.digest = true

  # Adds additional error checking when serving assets at runtime.
  # Checks for improperly declared sprockets dependencies.
  # Raises helpful error messages.
  config.assets.raise_runtime_errors = true

  # Raises error for missing translations
  # config.action_view.raise_on_missing_translations = true
end

Here is the top of my assets/stylesheets/application.css file:

/*
 * This is a manifest file that'll be compiled into application.css, which will include all the files
 * listed below.
 *
 * Any CSS and SCSS file within this directory, lib/assets/stylesheets, vendor/assets/stylesheets,
 * or any plugin's vendor/assets/stylesheets directory can be referenced here using a relative path.
 *
 * You're free to add application wide styles to this file and they'll appear at the bottom of the
 * compiled file so the styles you add here take precedence over styles defined in any styles
 * defined in the other CSS/SCSS files in this directory. It is generally better to create a new
 * file per style scope.
 *
 *= require_tree .
 *= require_self
 */

As well as the top of application.js:

// This is a manifest file that'll be compiled into application.js, which will include all the files
// listed below.
//
// Any JavaScript/Coffee file within this directory, lib/assets/javascripts, vendor/assets/javascripts,
// or any plugin's vendor/assets/javascripts directory can be referenced here using a relative path.
//
// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
// compiled file.
//
// Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
// about supported directives.
//
//= require jquery
//= require jquery_ujs
//= require_tree .

Edit: I should add that this only became a problem once I removed bootstrap...

To solve the issue:

rake assets:clobber

OR

delete the public/assets folder

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