config: simplify structure

* Replace `require_relative` with `require`
  The project tries to use the `require` form everywhere where possible, which
  is the common form
* `require` from `pry.rb`
  Spreaded `require` statements where we require internal classes is confusing
* Fixed namespace definition for Config classes
  https://github.com/rubocop-hq/ruby-style-guide#namespace-definition recommends
  to use explicit nesting

lib/pry.rb

@@ -113,6 +113,12 @@ require 'pry/command_set'
 require 'pry/commands'
 require 'pry/plugins'
 require 'pry/core_extensions'
+require 'pry/basic_object'
+require 'pry/config/behavior'
+require 'pry/config/memoization'
+require 'pry/config/default'
+require 'pry/config/convenience'
+require 'pry/config'
 require 'pry/pry_class'
 require 'pry/pry_instance'
 require 'pry/cli'

lib/pry/config.rb

@@ -1,11 +1,9 @@
-require_relative 'basic_object'
-class Pry::Config < Pry::BasicObject
-  require_relative 'config/behavior'
-  require_relative 'config/memoization'
-  require_relative 'config/default'
-  require_relative 'config/convenience'
-  include Pry::Config::Behavior
+class Pry
+  class Config < Pry::BasicObject
+    include Behavior
+
     def self.shortcuts
       Convenience::SHORTCUTS
     end
   end
+end

lib/pry/config/behavior.rb

@@ -1,4 +1,6 @@
-module Pry::Config::Behavior
+class Pry
+  class Config < Pry::BasicObject
+    module Behavior
       ASSIGNMENT = "=".freeze
       NODUP = [TrueClass, FalseClass, NilClass, Symbol, Numeric, Module, Proc].freeze
       INSPECT_REGEXP = /#{Regexp.escape "default=#<"}/
@@ -212,6 +214,7 @@ module Pry::Config::Behavior
       end
 
       private
+
       def __clip_inspect(obj)
         "#{obj.class}:0x%x" % obj.object_id
       end
@@ -248,3 +251,5 @@ private
         @lookup.delete(key)
       end
     end
+  end
+end

lib/pry/config/convenience.rb

@@ -1,4 +1,6 @@
-module Pry::Config::Convenience
+class Pry
+  class Config < Pry::BasicObject
+    module Convenience
       SHORTCUTS = [
         :input,
         :output,
@@ -13,7 +15,6 @@ module Pry::Config::Convenience
         :extra_sticky_locals
       ]
 
-
       def config_shortcut(*names)
         names.each do |name|
           reader = name
@@ -23,3 +24,5 @@ module Pry::Config::Convenience
         end
       end
     end
+  end
+end

lib/pry/config/default.rb

@@ -1,6 +1,8 @@
-class Pry::Config::Default
-  include Pry::Config::Behavior
-  include Pry::Config::Memoization
+class Pry
+  class Config < Pry::BasicObject
+    class Default
+      include Config::Behavior
+      include Config::Memoization
 
       def_memoized({
         input: proc {
@@ -135,6 +137,7 @@ class Pry::Config::Default
       end
 
       private
+
       def lazy_readline
         require 'readline'
         Readline
@@ -147,3 +150,5 @@ class Pry::Config::Default
         raise
       end
     end
+  end
+end

lib/pry/config/memoization.rb

@@ -1,4 +1,6 @@
-module Pry::Config::Memoization
+class Pry
+  class Config < Pry::BasicObject
+    module Memoization
       MEMOIZED_METHODS = Hash.new {|h,k| h[k] = [] }
 
       module ClassMethods
@@ -42,3 +44,5 @@ module Pry::Config::Memoization
         MEMOIZED_METHODS[self.class]
       end
     end
+  end
+end

lib/pry/pry_class.rb

@@ -1,4 +1,3 @@
-require 'pry/config'
 class Pry
 
   HOME_RC_FILE =