title: How to destroy and reinstall a Gem after migration?
body: <p>I would like to know how I can destroy a gem completely and reinstall it. </p>
  
  <p>This is what I did to install a gem called 'spree_fancy':</p>
  
  <pre><code>$bundle install 
  $bundle exec rails g spree_fancy:install
  </code></pre>
  
  <p>And resulted following: </p>
  
  <pre><code>bundle exec rails g spree_appa:install 
  
  append  app/assets/javascripts/store/all.js
        append  app/assets/javascripts/admin/all.js
        insert  app/assets/stylesheets/store/all.css
        insert  app/assets/stylesheets/admin/all.css
           run  bundle exec rake railties:install:migrations FROM=spree_appa from "."
  Copied migration 20140105025133_add_slider_taxons_and_apply_them.spree_appa.rb from spree_appa
  Would you like to run the migrations now? [Y/n] y
           run  bundle exec rake db:migrate from "."
  
  ==  AddSliderTaxonsAndApplyThem: migrating ====================================
  ==  AddSliderTaxonsAndApplyThem: migrated (0.3630s) ===========================
  </code></pre>
  
  <p>I have tried couple of different methods but didn't work: </p>
  
  <pre><code>$ bundle exec rake db:rollback
  $ rails destroy controller user_controller(controllerName)
  </code></pre>
  
  <p>I didn't destroy model, because the gem I'm using is a theme for Spree Commerce and doesn't include any model. I'm not sure how I can destroy a gem after I migrated bunch of files. </p>