Remove Spork and Guard

Use Zeus, Commands, or Spring instead:

https://github.com/burke/zeus
https://github.com/rails/commands
https://github.com/jonleighton/spring

They are superior to Spork for the following reasons:

* You don't have to commit anything into your Gemfile, spec/spec_helper,
  or version control.
* They improve the Rails bootup speed of rails server, runner, generate,
  console, and rake tasks... not just tests.

lib/suspenders/app_builder.rb

@@ -176,8 +176,8 @@ def configure_capybara_webkit
       end
     end
 
-    def setup_guard_spork
-      copy_file 'Guardfile', 'Guardfile'
+    def generate_clearance
+      generate 'clearance:install'
     end
 
     def setup_foreman

templates/Gemfile_clean

@@ -26,8 +26,6 @@ group :development do
 end
 
 group :development, :test do
-  gem 'guard'
-  gem 'guard-spork'
   gem 'rspec-rails'
   gem 'sham_rack'
 end