rubocop fixes...this feels sloppy in a way I don't fully understand yet

* It's not clear to me at all where we should hide the Application instance...or honestly right now where exactly it is hanging off the main object
  (if that's the right nomenclature).

examples/demo/app.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'prubot'
 
 on 'test-event', 'say howdy' do

examples/register/app.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'prubot'
 
 on 'test-event', 'say howdy' do

lib/prubot.rb

@@ -37,7 +37,7 @@ def run!
     end
 
     def run?
-      $0 == 'app.rb' # HACK HACK HACK need to decide how we want to handle this.
+      $PROGRAM_NAME == 'app.rb' # HACK: HACK HACK need to decide how we want to handle this.
     end
 
     def register_event(name, event, action = nil, &block)
@@ -56,8 +56,10 @@ def setup_routing
     end
   end
 
+  ##
+  # Prubot DSL
   module DSL
-    @@app = Prubot::Application.new
+    @@app = Prubot::Application.new # rubocop:disable Style/ClassVars
 
     ##
     # Supports both +on 'event' 'description' do...+ and +on 'action', 'event', 'description' do...+
@@ -70,12 +72,13 @@ def on(*args, &block)
       when 3
         @@app.register_event(args[2], args[1], args[0], &block)
       else
-        raise Prubot::Error 'on supports either "on <event> <description> do..." or "on <action> <event> <description> do..."'
+        raise Prubot::Error 'on supports either "on <event> <description> do..." or '\
+        '"on <action> <event> <description> do..."'
       end
     end
 
     at_exit { @@app.run! if @@app.run? }
   end
 end
 
-extend Prubot::DSL
+extend Prubot::DSL # rubocop:disable Style/MixinUsage

lib/prubot/dispatcher.rb

@@ -23,7 +23,7 @@ def call(env)
 
     private
 
-    def register_app(request)
+    def register_app(_request)
       [200, { 'Content-Type' => 'text/html' }, ['howdy']]
     end
 
@@ -35,7 +35,6 @@ def handle_event(request)
       generate_response event, action, result
     end
 
-
     def skip_verify?
       @config.secret == false
     end

spec/spec_helper.rb

@@ -4,7 +4,7 @@
 require 'prubot'
 
 RSpec.configure do |config|
-  # HACK HACK HACK clean up environment after every test (sigh)
+  # HACK: HACK HACK clean up environment after every test (sigh)
   config.after  { ENV.delete_if { |k, _v| k.start_with?('PRUBOT') } }
   # Enable flags like --only-failures and --next-failure
   config.example_status_persistence_file_path = '.rspec_status'